#90444: A Review of Interventional Radiology

Diagnostic radiology has historically been the backbone of any radiology department. In this area, general imaging techniques are employed and the most patients are seen. Procedure times range from just a few minutes (e.g., chest x-ray) to several hours (e.g., small bowel series), and from simple to complex. From automobile accidents to kidney stones and from strokes to abdominal pain, the diagnostic x-ray department is where it all starts. Initial screening is performed here, as are more sophisticated and more detailed procedures.

It is in this hospital department that many patients are given barium orally or rectally or have dyes and contrast agents instilled via tubes or drains to outline specific wound sites or follow the resolution of an abscess. They may receive intravenous x-ray contrast or have it injected through various fistulas or stomas. The diagnostic x-ray division has a rapid patient turnover, and the results often guide the next step, whether it be further testing or curative treatment.

It is important to note which dyes or contrast media have been used in the initial studies so that they may be considered prior to beginning more advanced or detailed procedures.

Rather than using x-rays to develop still images on a film that required processing time, early 20th century Edison fluoroscopes projected x-rays through the target and onto a tungsten metal-salt coated screen that fluoresced when excited by various levels of radiation, thereby producing a live-action image. The radiologist would sit behind the viewing screen, directly in the radiation field. Soon after the invention of television, TV cameras were the eyes behind the fluorescent screen. In modern fluoroscopes, x-rays are passed through the target and are collected by a phosphor intensifier, then digitally recorded and transmitted as moving images to a viewing screen. Contrast agents are used to enhance studies of soft tissues.

In the past, fluoroscopy was thought to be safe enough to use for shoe fitting in footwear stores. That proved to be incorrect. The medical benefit of fluoroscopy, however, outweighs the risks of prolonged x-ray exposure (e.g., radiation burns, cancer) [2]. Many newer devices allow for pulsed radiation and freeze-frame viewing, reducing radiation exposure to the patient and the staff.

Formerly known as computerized axial tomography (CAT), the newer machines employ various imaging methods that allow the clinician to view cross-sectional and three-dimensional images of the body through scans taken from different angles and varying depths. The newer CT scanners are more patient friendly. The patient lies on a table that is moved into the center of the scanner. After the camera is positioned, the x-ray tube moves around the opening as it obtains images. The scanner takes a series of rapid readings, then a computer generates an exact model of the area, showing excellent detail [3].

The CT scanner is an extremely fast machine compared to magnetic resonance imaging (MRI). Its ability to produce images of the body with great precision has revolutionized competency and speed of diagnosis and often gives an immediate answer to the question of what is happening in areas of the body that routine x-rays cannot see. Emergency departments rely heavily on the CT scanner to aid in the diagnosis of many patients; in fact, many emergency departments have their own units. Patients who undergo CT scanning of the abdomen and/or pelvis often ingest a barium type solution to highlight the digestive tract. Most patients are also given an iodine-based intravenous contrast injection that enhances the images and shows details of suspicious areas that otherwise might be missed. Some estimates of the number of intravascular administrations of a radio-opaque contrast medium exceed 10 million procedures per year in the United States alone. Of this number, a relatively large percent of exams are in the area of CT scanning.

One benefit of MRI is that it is accomplished without the use of x-rays. The old name, nuclear magnetic resonance, was dropped because this modality has nothing to do with radioactivity and the word "nuclear" frightened some patients. The process involves a large, powerful magnet, radiofrequency (nonionizing) emissions, and computer analysis [4].

In simplest terms, when the human body is placed in a strong magnetic field, hydrogen atoms and molecules inside the body are affected. The computer picks up the movement and converts it to a very detailed image.

The first MRI units were closed magnets that were shaped like tunnels, with openings on both ends and open spaces in the sides. However, an increasing number of new MRI units are more open, making them less uncomfortable for the patient. The quality of most of these scanners comes close to that of the tunnel-like units. An average test may take anywhere from 20 minutes to one hour or more. While the scan is in progress, a loud banging noise is usually audible to the patient, which is caused by the equipment and changing magnetic fields.

Because of the strong magnetic field, no objects that can be attracted by a magnet can be brought into the MRI room, and there are various relative and absolute contraindications for the examination. The magnet may affect devices such as cardiac pacemakers, internal defibrillators, and implanted nerve stimulators unless the devices are specifically magnetic resonance (MR) conditional. MR conditional devices allow patients to safely undergo MRI as long as the machine is correctly calibrated. However, so patients with non-MR-conditional devices are excluded from undergoing MRI exams. The same holds true for most aneurysm clips because the magnetic field may cause some of them to move or twist, an event that could prove catastrophic. Therefore, before beginning any MRI exam, patients should fill out a detailed medical history form for their protection. MRI provides detailed anatomic images, and it is excellent for the diagnosis of soft tissue abnormalities.

Many studies are enhanced by the intravenous injection of contrast agents that are specific for MRI examinations. These are commonly dyes based on gadolinium, a paramagnetic, rare-earth chemical element. In 2006, the U.S. Food and Drug Administration (FDA) issued a public health advisory regarding gadolinium-based contrast agents (GBCAs) because of the development of nephrogenic systemic fibrosis (NSF) in 25 patients with acute or chronic severe renal insufficiency; by December 2006, 69 cases were reported to the FDA [5,6]. The advisory has since been updated, and the FDA has mandated a boxed warning describing the risk of NSF on all nine GBCAs available in the United States [7,8]. The 2010 update states that GBCAs increase the risk for the development of NSF among patients with severe renal insufficiency or renal dysfunction. The FDA has not received reports of NSF among patients with normal renal function or moderate renal insufficiency [7]. The symptoms of NSF are [7,9,10]:

There is presently no treatment for NSF, which worsens over time and can cause death; however, kidney transplantation can slow or halt the condition [7].

In 2015, the FDA began investigating the risk of deposits of GBCAs in the brains of some patients following repeated use of GBCAs [8]. The investigation is based on reports in the literature that specifically site GBCA deposits in the brains of some patients who had undergone four or more contrast MRI scans. The deposits appeared long after the last administration of the contrast agent. In 2017, the FDA began requiring a new class warning and other safety measures for all GBCAs for MRI concerning gadolinium remaining in patients' bodies, including the brain, for months to years after receiving these drugs [11]. The retention of gadolinium has not been directly linked to adverse health effects in patients with normal kidney function, and the agency concluded that the benefit of all approved GBCAs continues to outweigh any potential risks [11,12]. In addition to approving the updated prescribing information concerning gadolinium retention, the FDA also approved new patient Medication Guides for all GBCAs. MRI centers should provide a Medication Guide the first time an outpatient receives a GBCA injection or when the information is substantially changed [11]. The FDA continues to recommend that healthcare professionals consider limiting GBCA use to clinical circumstances in which GBCA use provides additional, necessary information [8].

Ultrasonography exams use sound waves to form images. The basic principle is the same as that of sonar or depth sounding in studies of the ocean. In diagnostic ultrasonography, the ultrasonic waves are produced by electronically stimulating a crystal transducer. After applying a small amount of a jelly-like substance over the area to be scanned, the technologist moves a transducer across the site. As the beam strikes an interface or boundary between tissues of varying density, such as blood and muscle, some of the sound waves are reflected back to the transducer as echoes. The echoes are converted into electrical impulses that present an image of the tissues under examination [9].

Ultrasound can be used to examine many areas of the body. Blood flow can be observed using color Doppler techniques as it courses through the veins, arteries, and heart. Normal and pathologic tissues can be seen, and fluid collections in the body cavities can be clearly demonstrated. Ultrasound can measure sizes and shapes of various organs and is very valuable as an aid in obstetrics and gynecology, where x-rays should be avoided. The technique can evaluate fetal size and maturity and fetal and placental position. It is also a fast, relatively safe, and reliable technique to diagnose multiple pregnancies. Aside from drinking a copious amount of water for scans in the pelvic region, there is no real preparation needed. Ultrasonography is painless and noninvasive, with the exception of transvaginal or transrectal probes that are sometimes used. For this reason, ultrasound is often the first exam ordered, in the hope of achieving a diagnostic answer as quickly and safely as possible. Ultrasound can diagnose tumors, aneurysms, and a vast array of disorders. An advance in ultrasound is 3-D imaging, which can convert still images into a lifelike display.

Concern has been expressed about the overuse of high-power 3-D ultrasound imaging and fetal exposure to high energy levels, especially in nonmedical settings. Some studies have shown that higher rates of conventional low-power prenatal ultrasound exposure to the fetus may be associated with delayed speech, increased incidence of left-handedness, fetal growth restriction, and low birth weight [13,14,15]. The FDA has recommended that all keepsake 3-D and 4-D (movie type) ultrasonography be avoided due to effects on the fetus [16,17]. It is recommended that prenatal ultrasound should be limited to brief exposure and only when medical benefit will be derived [16].

Although it is occasionally a separate department, the nuclear medicine section uses radioisotopes for diagnostic and therapeutic purposes. These compounds are given orally or intravenously and are tracer agents for the areas to be studied. The tissue targeted "picks up" the injected isotope, which is then tracked by imaging or scanning equipment. In that regard, nuclear medicine differs from diagnostic radiology; the radiation is within the patient and is detected by the external device. Although the administered materials are radioactive, they are very low level and are excreted safely and quickly from the body. Some tests are carried out immediately after the injection, but others require a wait of several hours or even days because various agents take different amounts of time to get to and settle in the areas or organs being studied.

Patients are usually scanned while lying down or sitting adjacent to a scintillation camera. Nuclear medicine studies can detect tumors, fractures, abscesses, arthritis, bleeding points, ischemic cardiac regions, and a multitude of other problems. Importantly, besides structure, these tests usually illustrate how the organs function. For example, renal scans show the structure and function of the kidneys and may be enhanced by giving certain medications during the studies. Lung scans detect emboli and other lesions by showing perfusion, which illustrates regional blood flow to the lungs, and ventilation, which compares it to airflow. For this test, the patient inhales a radioactive gas to show ventilation and also receives an intravenous injection to outline pulmonary perfusion. Nuclear cardiology studies, in which various types of cardiac scans are performed, have become very popular. For example, the exams can show perfusion of the heart muscle before and after increased stress caused by treadmill exercise or induced by inotropic drugs. Studies are available to image the functioning of brain tissue (e.g., positron emission tomography [PET] scanning), which has become an important step in attempting to diagnose Alzheimer disease [18].

After their diagnostic procedures, patients need not take any special precautions and are not considered to be significantly radioactive. Half-lives of these agents are short, but patients may be encouraged to drink extra fluids to minimize the amount of contact the isotopes have with the urinary bladder. Some patients may be advised not to hold small infants until the radioactive tracer is out of their system.

Known as the operating room of the radiology department, interventional radiology has expanded greatly. Sometimes referred to as the special procedures division, interventional radiology is staffed by personnel trained to conduct invasive procedures, biopsy deep internal organs, drain abscesses and cysts, open blocked arteries and veins with devices or medications, and provide a means by which obstructed kidneys and biliary tracts may be emptied. Rather than an area of screening, interventional radiology is usually where patients end up for therapeutic procedures, often after several other diagnostic studies.

For example, a patient with abdominal pain and jaundice may have undergone extensive x-rays, ultrasound, CT, MRI, and biliary scans, only to find him or herself on the interventional radiology table undergoing a percutaneous transhepatic cholangiogram that will drain blocked bile ducts and relieve symptoms. It is this area of practice that has revolutionized much of patient care and treatment and is the basis for the material contained in this course. The remainder of this course will focus on the types of procedures performed and their associated benefits and possible disadvantages.

Biopsies have been performed at the bedside for many years. With the aid of procaine and a sampling needle, the physician was able to "blindly" take a sample of tissue, such as the liver, that was sent to the laboratory for analysis. It was not until cross-sectional imaging became available in the 1970s that the diagnostic potential of needle biopsy was fully appreciated. Today, interventional radiology percutaneous biopsies can diagnose primary or metastatic malignancy, tumor recurrence, and staging, infection, and other disorders [37].

The art of CT, MRI, ultrasound, or fluoroscopy now allows the great majority of tissue abnormalities to be safely sampled [37]. The success and risk of needle biopsy procedures depend on a number of factors. The patient should be reasonably capable of cooperating during the procedure; for example, the patient should be able to remain totally still and not breathe during needle placement. The area being sampled should be readily identifiable on the image, and the clinician should be skilled at the procedure, able to avoid major blood vessels, the bowel, and other potentially hazardous areas.

To make an accurate diagnosis, the specimen should be handled properly. It should be taken directly to the cytopathologist, although more often the pathologist, or a staff member, comes directly into the interventional radiology room to care for the specimens. According to the working diagnosis, care should be taken to ensure that the tissue is sent for culture and appropriate staining. Having the pathologist present is immensely helpful to determine what types of additional studies might be indicated. The radiologist usually obtains several tissue samples as multiple specimens increase accuracy.

Organ biopsy may be performed under ultrasound guidance, which has been shown to produce good results in some small abdominal and pleural lesions. In some cases, however, it may be difficult to visualize the tip of the biopsy needle, but this modality is preferred by some interventional radiologists. Fluoroscopy with C-arm may also be used for biopsy procedures. This technique is capable of helping the physician determine accurate needle placement. CT is used when biopsying deep lesions and can guide the operator past large blood vessels or intestines. CT scanning provides the most anatomic detail and can be used to plot a safe pathway to the lesion. The new scanning modalities and sampling needles have made the procedure faster and more precise.

Most often, the patient who presents for biopsy has already undergone a diagnostic CT scan, ultrasound, or MRI. The films are ready, and the desired and detailed approach to the procedure has already been determined. If there is any uncertainty at the beginning of the case, the scan may be repeated with or without intravenous contrast agents. Oral contrast material, which is given for CT scans of the digestive system, may also be indicated at that time if there is any question concerning the area involved.

Biopsies involving a specific area or small lesion take somewhat longer and are a bit more involved than those involving a random sample of a tissue. Examples of general organ biopsies include a liver biopsy to diagnose or stage hepatitis C or a kidney biopsy to determine amyloidosis.

Tissue sampling techniques vary, but general principles remain constant. There are many different versions of sampling needles, but all should be able to permit recovery of enough material to allow both cytologic and histologic studies. The needles should be sharp enough to enter small, hard lesions without pushing them aside. The choice depends upon the kind of imaging modality used, the type and location of the lesion, and perhaps most importantly, the preference of the clinician. Biopsies are performed in short steps, no matter which type of guidance has been selected. In all cases, the skin is numbed with an anesthetic, such as lidocaine 1%, followed by infiltration of the deeper tissue. A small puncture with a scalpel may be made to aid the passage of the needle, which is inserted and followed by imaging to check for placement. Several sequential images assure that the needle is in place in the desired target tissue.

Chest Biopsy

The American College of Radiology states that definitive diagnosis of a mediastinal mass by biopsy is vital in that it may significantly change the treatment options or may preclude the need for exploratory surgery. Image-guided biopsies of mediastinal masses are almost always performed using CT guidance.

(https://acsearch.acr.org/docs/69343/Narrative Last Accessed: June 1, 2022)

Level of Evidence: Expert Opinion/Consensus Statement

Improved imaging capabilities and biopsy techniques have made it possible to obtain tissue samples from most lung lesions, including some that measure less than 1 centimeter in diameter. Bronchoscopy is performed for central endobronchial lesions, but percutaneous needles can safely approach most other thoracic masses. Needle biopsy of the thorax is performed when there is a reasonable suspicion of malignancy, to confirm what appears to be a benign lesion, to obtain samples of what seems to be infectious material, and to aid in staging patients with neoplastic extension to the hilum, mediastinum, or chest wall. False negative results have been reported, but taking multiple samples from different parts of the lesion may reduce these numbers. Depending on many factors, these false negatives may be followed by a repeat needle biopsy, open lung biopsy, or watchful waiting with regular, periodic chest x-rays [38].

How the patient is positioned during lung biopsy depends on the location of the lesion and the path the radiologist uses to reach it. The patient may be positioned on his or her back, with the head elevated slightly and arms supported above the head, or prone with the head turned to the side and the arms stretched upwards. Patients are made as comfortable as possible during the procedure and soft restraints or armbands are applied to provide comfortable positioning of the extremities.

The most common complications from thoracic biopsy are collapsed lung (pneumothorax) and minor bleeding leading to coughing blood (hemoptysis). It is not uncommon for patients to cough up bright red blood for several hours after their procedure, and they should be warned that this may occur. Hemoptysis usually subsides spontaneously. A chest x-ray is almost always performed within 15 minutes after biopsy of the thorax to be sure that there is no pneumothorax. Some studies have found an overall frequency of pneumothorax of between 9% and 54% (with an average of around 20%), but many of these are small areas and require no treatment [39]. The single most important factor contributing to pneumothorax does not appear to be needle size, but rather the presence of chronic obstructive pulmonary disease (COPD), small lesion size, a long needle path, and repeated pleural puncture [39].

Most radiologists believe that treatment of a postbiopsy pneumothorax rarely requires a large chest tube but can easily be treated initially by the radiology department. A small (size 6 to 9 French) trocar catheter is inserted into the pleural cavity through the anterior second or third intercostal space in the midclavicular line and is connected to a one-way Heimlich valve. Usually the air leak will seal within 12 to 48 hours and does not require connection to suction. The patient most often will be admitted to the hospital, but in select cases reliable outpatients will be allowed to go home with the tube in place and return the following day for re-evaluation.

The development of cross-sectional imaging has made it possible to perform drainages of deep body cavities without subjecting the patient to open surgery. Abdominal, pelvic, or other soft tissue fluid collections and abscesses may be safely approached and drained by percutaneous catheters. Depending on the diagnosis and site of fluid collection, the interventional radiologist most often can predict whether a drainage catheter is going to be left in place or if the entire area is going to be drained and the catheter removed. Percutaneous drainages are most often performed under CT scan or ultrasound guidance; fluoroscopy is used less frequently. Drainages are often performed simply for diagnostic aspiration. Specimens are withdrawn and sent to the laboratory for culture and sensitivity, cytology, and multiple chemistry analyses. Tests such as these can aid in making the diagnosis of abscess, hematoma, biloma, and malignancy.

There are some instances in which fluid may be obtained as a bedside procedure, without the need for imaging techniques. Bedside paracentesis and thoracentesis are relatively common events in all hospitals, but there are many situations where these routine procedures are not possible. For example, obese patients benefit from radiologic guidance because the patient's abdominal pannus often presents a difficult or even impossible mechanical obstruction to the sampling needle. Large tumor masses may also pose problems for the operator. It may be unsafe to attempt penetration of the abdominal cavity with areas of vascular tissue situated in the space to be entered. Care always should be taken to avoid bowel, spleen, and major blood vessels. Puncturing the diaphragm may lead to serious problems for the patient, so the clinician should be aware of the individual patient's anatomy. As a result, it has become increasingly common for physicians to ask the interventional radiologist to perform abdominal fluid sampling and drainage of ascites under the guidance of the ultrasound or CT scan.

While it is often possible to drain a large area of abdominal fluid with one drainage catheter or needle, the CT or ultrasound image may point to several multilocular sites, which would require more than one puncture. Sometimes in cases such as these, especially when abdominal abscesses are present, the recommendation is to take the patient to the operating room and perform a surgical incision and drainage with abdominal irrigation. The same is true for abscesses that have formed around infected surgical grafts. It is common, however, for the radiologist to drain two areas of fluid collection at the same time when the pockets of material are not connected and massive contamination is not suspected.

There are times when the fluid is found to be so viscous that draining presents a problem. While it is possible to irrigate through the catheters or instill medication to make the fluid less viscid, the overall results in these cases are usually less than optimal. All drainage procedures involve the same basic preparations as are required for biopsies. Histories, clinical assessments, and laboratory and chart reviews are standard. Anything pertinent to the case is evaluated and discussed before the procedure starts. Patients are either kept fasting or allowed only clear liquids. The skin is prepped and draped, and local and deep infiltration is performed with 1% lidocaine; moderate sedation is administered as necessary [47].

A surprising percentage of the population has undetected visceral cysts, many of which are located in the kidney, liver, and pancreas. Although most cysts go unnoticed until discovered accidentally during an unrelated imaging procedure, some grow large enough to cause symptoms. An interventional procedure may be recommended when symptoms arise or when a particular cyst appears suspicious.

Hepatic cysts, unless due to infections, very large, or multiple, usually have no real clinical significance and are found mainly on CT scans or other imaging procedures. Cysts in kidneys may be of several types and may vary in size from less than 1 centimeter to more than 10 centimeters in diameter. A person may have multiple cysts, such as in polycystic kidney disease, or isolated cysts arising from the renal cortex or medulla. Some cysts are of hereditary origin while others have an inflammatory or neoplastic etiology.

The ability to perform percutaneous nephrostomy (PCN) has led to an entirely new approach to the treatment of urologic disease. First used solely for the decompression of obstructed upper urinary tracts, it now can be used to obviate open surgery, which is usually accompanied by protracted recovery periods. Even the advent of extracorporeal shock-wave lithotripsy (ESWL) has not eliminated the need for the percutaneous approach to the collecting system of the urinary tract for some patients with kidney stones [66,67,68].

PCN provides a less invasive means to drain the renal collecting system in cases where obstruction of the kidney and ureter has resulted in hydronephrosis. Most often used for patients with kidney stones or bladder or pelvic tumor obstructions, PCN may be used to divert urine from the renal collecting system to allow leaks and fistulas to heal [67]. The procedure is often performed after attempts at placing a ureteral stent through retrograde cystoscopy have proven unsuccessful. Hence, it is vital that the urologist and radiologist consult and work as a team. In cases of ureteral obstruction, radiographic images often show an obstructive hydronephrosis. Providing drainage for that kidney is an urgent necessity, and PCN provides an exact method of accomplishing this task.

The access provided by nephrostomy allows ureteral strictures to be dilated and stents to be placed as needed. The stent provides a means to hold open an area that is contracted or constricted. PCN provides a means by which infected urine may drain and the reflux and damage caused by the obstruction may be relieved. Before performing PCN, the patient will have undergone several procedures to obtain the most information possible. Ultrasound of the kidney and an IVP will most likely have been performed, possibly along with nuclear medicine and CT scans [67].

It is sometimes difficult for the patient and family to grasp the concept of PCN, so the radiology staff, including physicians, should begin with a basic discussion of the anatomy and physiology of the genitourinary system. By explaining to patients that the kidney makes urine and that it drains down through the ureters into the bladder, they should be able to understand the importance of providing an outlet for such drainage. Patients and family should realize that PCN is not a one-step procedure that will result in an end to the problem; it is a part of the entire therapeutic intervention, which may take several days or weeks to complete.

To stress the need for teamwork between the interventional radiologist and the urologist, it should be understood that the removal of multiple stones in the renal collecting system depends on the point of entry of the nephrostomy tube. Once the kidney drainage has been established in the radiology department, the urologist is able to proceed with stone removal in the operating room via the PCN tract. In some instances, the interventional radiology team goes to the operating room and the first part of the procedure is performed on the operating table, with portable fluoroscopy as the guidance mechanism.

Patients undergoing PCN should be treated with antibiotics and should receive an intravenous dose within one hour of the procedure being initiated [67]. There is a high incidence of septic shock in patients with upper urinary tract infection, even with antibiotic prophylaxis. Because kidney stones are commonly associated with infection, premedication with antibiotic therapy is commonly used when stones are thought to be present. The most common urinary pathogens are gram-negative bacteria, thus administration of the antibiotic is continued for at least 48 hours after the procedure. Nephrostomy tube placement is most often performed with local anesthesia along with IV moderate sedation. General or epidural anesthesia is indicated only if extensive tract dilatation is planned prior to stone removal.

The approach is extremely important for PCN, and the procedure is performed under ultrasound or fluoroscopic guidance. In some cases, a small amount of intravenous iodinated contrast is administered at the start of the procedure to opacify the collecting system [67]. The patient is placed in the prone position with both arms above his or her head or one arm up and the other at the noninvolved side. The entry site is prepped and draped and infiltrated with local anesthetic. A small puncture is made with a scalpel, and a posterior lateral approach is made with a needle and directed toward a lower calyx of the kidney. If the tip of the needle has entered a dilated part of the collecting system, urine will flow back from the needle when the stylet is removed. A specimen should be collected and sent to the laboratory for microscopic and bacterial studies. Obviously, infected urine will be cloudy and turbid.

Once the proper position is established, various wires and dilators are used until a nephrostomy tube can be passed into position. The catheter is meticulously secured in place and attached to a properly labeled drainage bag [67]. It is normal for hematuria to be present after the procedure and to continue for one to two days. Explicit orders should be written in regard to tube output and maintenance.

Depending on the diagnosis, patients may be discharged within several days after undergoing PCN. Many cancer patients who have had palliative nephrostomies go home with the catheters in place and most often are seen by a visiting nurse. Flushes with 5 cc of sterile saline may be ordered to ensure free flow of urine [67]. Tube changes may be scheduled every 6 to 12 weeks or more frequently if conditions warrant. If the PCN is for decompression, the external drainage may be continued until the desired results are achieved and urine begins to flow naturally down the ureter. Nephrostomies that are performed for future stone removal may have the drainage part plugged until it is time for the procedure to be performed.

Hemorrhage is the major risk of PCN, but the risk can be reduced substantially with use of a very small needle. Nephrostomies are performed frequently in interventional radiology departments and are a major part of the treatment for patients with malignant obstructions, renal stones, and other kidney problems [67,69].

Ureteral stents are frequently inserted when there is a need to provide a means of holding open a stenosed portion of the ureter. Ischemia is the most common of many causes for these strictures and may result from a variety of reasons, including pressure necrosis from a ureteral stone, trauma, radiation therapy, surgical manipulation of the ureter, inflammatory disease, and chronic transplant rejection. All of these scenarios result in a diminished blood supply to the area and can initiate a cycle of ischemia, scarring, and greater ischemia.

Before patients are referred for PCN, they have almost always undergone prior urologic procedures whereby the urologist has attempted to open an obstructed ureter and establish free urine flow. A urologic stent is often placed during the cystoscopy to bypass the obstruction, but a nephrostomy is indicated when the kidney must be drained from above. PCNs are often followed by ureteral stent placement.

Certain areas of the ureter may be amenable to balloon dilation, but ureteral stenting often produces a more positive result. Stents of 6 to 8 French are commonly used for placement in ureters. While there are many types and styles of ureteral stents, and many new designs under evaluation, the most common is a polyurethane double pigtail device [70].

Stents are passed into the tract over a guide wire with a type of pushing catheter. When it is in the proper position, the stiffener is removed, the nephrostomy tube is replaced, and the guide wire is removed. It is often advisable to leave the draining nephrostomy catheter in place for one to two days after internal stent placement to allow draining urine to flush normal operative debris from the newly placed stent.

Nephrostograms, using a dye or contrast through the nephrostomy tube to assess the condition of the ureter and implanted stent, should be performed as a follow-up procedure. When the radiologist is confident that the stent is open and urine is flowing freely, the nephrostomy tube is usually removed. The patient is left with a functioning urinary system with a ureter that will hopefully remain open for a long time. The procedure leaves no external signs of any manipulation, except the small wound that should quickly begin to heal.

As healing occurs, the urologist may determine that it is time for the stent to be removed. Stent removal does not necessitate another PCN; it may be removed in the cystoscopy room with urologic instruments. In cases in which the stent must remain in place for longer periods of time, the urologist may be able to change it and place a new one through a retrograde cystoscopy procedure. Patients with malignant obstruction of the ureters must have their stents changed for the duration of their lives [71].

Percutaneous transhepatic cholangiogram (PTC) or transhepatic cholangiogram is used to establish drainage of the biliary system. The procedure is commonly performed in the interventional radiology area and obviates the need for open major abdominal surgery. This procedure is often palliative and is frequently performed on patients with nonresectable malignant disease but may occasionally be indicated for patients obstructed with gallstones [72]. It may be contraindicated, though, for patients with diffuse hepatic metastasis, liver failure, or a life expectancy of only days to weeks.

This procedure may also be indicated to treat strictures that cannot be reached during endoscopy and may be of benefit to provide preoperative drainage of bile in patients with severe active cholangitis. PTC may help clinicians predict which biliary tumors are considered inoperable. Many patients not able to be cured surgically may do well for comparatively long periods of time with the placement of a drainage catheter. Some patients are discharged with biliary catheters in place and are up and about rapidly. Much of the discomfort and aesthetic problems associated with severe jaundice and the pruritus it produces may disappear or be greatly diminished. PTC may also shorten the hospital stay and give the patient an improved quality of life.

The patient should be premedicated with intravenous antibiotics for at least one hour prior to the transhepatic cholangiogram. Special attention should be paid to PT, INR, and PTT results because patients with liver disease often will have abnormal coagulation studies [72]. The patient should understand the procedure and realize that he or she will likely have to wear a bag to drain bile following the PTC or transhepatic cholangiogram.

Liberal doses of sedatives and opioids are given, because transhepatic cholangiogram is an uncomfortable procedure. For the procedure, the skin and subcutaneous tissues are infiltrated with lidocaine 2% and a small nick is made with a scalpel blade. The interventional radiologist selects the level at which to place the needle between adjacent ribs, taking care not to go near the lung. The long needle is guided into the liver by fluoroscopy, and the exact position is determined by instillation of contrast material [72]. Studies have supported the use of extravascular contrast-enhanced ultrasonography as an alternative to fluoroscopy [73,74].

Once the operator is certain that the needle is positioned in a duct adequate for biliary drainage, various wires and introducers are exchanged until the proper drainage catheter is in place. Bile may be sent to the laboratory for culture and sensitivity, and the dressings and drainage bag are secured completely, keeping in mind both the safety of the catheter and the comfort of the patient.

In some cases, it is not possible to pass a tight obstruction on the first attempt [72]. It has been found that if the tract is allowed to rest, it may decompress, allowing success several days later. If a stricture due to tumor or stenosis can be opened, internal drainage of bile is made possible and the patient no longer has to wear a bile-collecting bag. The bile is able to drain directly into the duodenum. Most radiologists, however, prefer to keep the system on external drainage for the first few days even if the obstruction is passed, to assure adequate biliary decompression. After the bile is clear and debris free, the catheter may be capped and internal drainage begun. Even if the catheter is not removed, patients may live relatively normal lives.

The catheters are usually changed about every four to six weeks in simple outpatient procedures in the same radiology suite. Patients may be placed on oral antibiotics before their catheter changes, but the tube change is relatively quick and easy for the patient.

Biliary stents may be inserted, but their use is most frequently seen in palliative terminal care [75]. Some patients find the presence of a catheter protruding from their abdomens and the occasional leakage of small amounts of bile totally unacceptable; for these patients, stents are a viable option.

The use of internal biliary stents depends on the preference of the patient and the physician, as well as the expected life span of the patient. In cases of nonresectable pancreatic tumors, stents will often remain open for the patient's remaining few months. For slow-growing tumors, however, this may not be the best answer because one of the disadvantages of a biliary stent is that a completely new percutaneous procedure must be completed if the stent becomes obstructed. That means the patient must be put through another long and invasive procedure, something that may not be acceptable with terminally ill patients.

Patients who undergo PTC may be sent home after just a few days in the hospital. Their symptoms are relieved, and they look better. This is a welcome alternative to prolonged hospitalization with or without major surgery and is just one other way in which interventional radiology helps patients to have beneficial results with minimum risk [76].

Endoscopic retrograde cholangiopancreatography (ERCP) is a procedure performed by gastroenterologists or other specialists; it often takes place in the fluoroscopy room of the radiology department. ERCP will be discussed in this course only briefly because physicians, nurses, and surgical support are usually from the operating room staff. However, radiologic technologists operate the imaging equipment, and interventional radiologic technologists sometimes offer assistance with difficult procedures.

ERCP involves passing an endoscope through the mouth, as in upper gastrointestinal endoscopy. The patient is either given IV moderate sedation by the operating room team or general anesthesia by an anesthesiologist or nurse anesthetist. A catheter is passed through the opening of the ampulla of Vater and contrast material is injected to visualize the ducts. Precise biliary and pancreatic anatomy may be identified, and depending on the findings, therapeutic procedures may be performed by the gastroenterologist.

Common bile duct stones may be removed, tight sphincters may be released, and certain bile duct strictures may be drained through endoscopic placement of tubes or stents. ERCP is not performed during an acute attack of pancreatitis unless the pancreatitis persists and a stone is thought to be responsible. As with other interventional procedures, coagulation and bleeding disorders are contraindications. Hemorrhage and pancreatitis, although uncommon, are possible complications of the procedure.

In many cases, ERCP has replaced surgery for gallstone removal. It is a same day procedure, and patients are discharged several hours later with little or no restrictions. They are up and able to resume their normal activities the following day, and many patients do so free of the gallstones that troubled them in the past.

Before discussing any procedures that concern the blood vessels, it is important to begin with a brief overview of vascular interventional radiology. Angiography has long been used as the general term for the radiographic examination of the blood vessels. These studies are used to image physiologic and pathologic changes in the anatomy by injecting a contrast agent into specific portions of the vascular system. The key word here is "specific," as angiography is almost always used to examine a specific anatomical region. Almost any part of the body can be imaged during the angiographic study. The brain, heart, lungs, chest, abdomen, kidneys, arms, and legs all possess a myriad of blood vessels that are accessible by skilled interventional radiologists.

Angiography is best defined as the visualization of the internal anatomy of the heart and blood vessels after the intravascular introduction of a suitable contrast agent. Typically, the contrast medium is introduced by an intravenous or intra-arterial injection or through a catheter that is inserted into a peripheral vessel and guided to the desired target area. With exams such as CT scans and IVP, similar contrast is injected, but the agent usually goes in through a peripheral vein and enters the general circulation. Nuclear medicine blood flow studies are also usually performed with injection of a radionuclide agent through a peripheral vein.

Before the discovery of x-rays, the injection of materials into the vessels of the body was performed primarily on cadavers for academic purposes. The procedure was limited to the injection of various dyes or waxes that stained the tissues of the body and facilitated the study of human anatomy after dissection. This practice was continued after Roentgen's discovery and extended to the introduction of radiopaque materials that permitted physicians and anatomists to record the anatomy with x-rays. The use of this technique was not successfully applied to live subjects until about 1920, when a contrast agent was developed that could be safely introduced into the vascular system.

Improvements in equipment and the development of safer contrast agents fostered research in angiographic procedures. Angiography became a safe, reliable diagnostic technique. The newly developed catheterization procedure provided a springboard for the use of angiography for therapeutic purposes. Specific area visualization is accomplished by accessing a vessel with a needle that introduces a catheter, and manipulating the catheter so that it arrives at the desired location. In the early days of angiography, the vessel had to be surgically exposed to accomplish this task, but in 1953, the Seldinger technique was developed and has become the basis for modern angiography. With this method, the femoral artery is punctured over the middle of the medial third of the femoral head. The common femoral artery is only 3–5 centimeters long but is usually easily accessed.

Several therapeutic radiologic procedures may be performed at the same time as the diagnostic study, although others can be performed as follow-ups on a subsequent day. All patients undergoing angiography should be carefully prepared, just as those having any type of invasive radiologic procedure. Patients are kept fasting, except for extra water, which they are asked to drink the morning of the procedure. This liquid, plus the intravenous fluids that are given, increases patients' hydration to help dilute the radiographic contrast material they will receive and to help prevent any possible renal dysfunction.

The usual patient selection and preparation principles are used. Angiograms are most often longer and more involved than other types of radiologic interventions, and the patient may have to remain on the table for hours at a time. To obtain high-quality images, it is imperative that patients lie absolutely still; consequently, they are often kept in position with a variety of soft restraints, belts, and bands. Depending on the type of study, they may be asked not to breathe, swallow, blink, or wiggle their toes.

Angiography can be tedious and exhausting for patients. Their arms are most often secured at their sides with wristbands to prevent them from inadvertently touching the long catheters or contaminating the sterile fields. Patients usually require repeated small doses of intravenous sedation, and they often sleep for short periods. However, patient cooperation during contrast injections is essential, and they are awakened to be monitored and provided with instructions.

In the standard procedure, the catheter is positioned in a specific location in the chosen blood vessel, and then pressure injectors shoot radiopaque dye directly into the catheter. Multiple images can be obtained as the contrast agent is injected. Patients may perceive a very warm or even hot sensation in the local area or along the region being studied, but the feeling disappears rapidly. With each injection, the interventional radiologic technologist tells the patient what is going to happen, reminds him or her not to move, and reassures that the warmth will go away. If catheters are positioned in vessels near or in the lower abdomen or pelvis, patients may get the feeling that they are urinating as the contrast enters that area. They should know in advance that this feeling may happen as many patients become upset and frightened by the thought that they have been incontinent.

Abnormalities in blood vessels cannot be repaired or altered until their exact anatomy is ascertained. The procedure allows one to follow the flow of blood through the lumens and see which vessels branch off other vessels, which have strictures, and which have limited blood flow. By following the stream of dye through the veins and arteries, it is possible to see vascular occlusive disease, aneurysms, arteriovenous malformations, and arteriovenous fistulae, as well as to diagnose and localize small vascular tumors. Preoperative assessment of vascular anatomy is provided, which is essential before organ transplants, revascularization, bypass graft procedures, and certain tumor resections can be performed.

Angiograms aid in the diagnosis and treatment of vascular complications of disease or surgery and are a means by which interventional radiology teams can perform percutaneous vascular interventional procedures such as angioplasties, embolizations, and infusions of certain therapeutic medications. As noted, many therapeutic procedures are performed in the radiology department during angiography. A great majority of these procedures have replaced open surgery. Similar to biopsies and drainages, they can spare patients general anesthesia and days or weeks of hospitalization.

Before undertaking any angiogram, the interventional team should assess all the patient's pulses, including axillary, brachial, radial, femoral, popliteal, and dorsalis pedis. Pulses are checked by touch as well as by Doppler to establish a baseline for the postprocedure observation and also to assist the radiologist in selection of the point of entry for the angiographic needle. Arteries are often deep in the tissues, and optimal entry sites are located by assessing the patient's pulse points along with the knowledge of normal anatomy.

Because the circulatory system is closed, with vessels branching or extending one from another, it is possible to selectively catheterize a vessel. For example, the renal artery may be entered, studied, and repaired through an opening made in the femoral artery. The approach chosen depends on the area to be examined, the patient's condition, and the angiographer's personal preference. During the procedure, the team should be prepared to handle any emergency that may occur and should strictly adhere to all established protocols. Most hospitals use specialized informed consent forms for angiography, such as that shown in Table 6.

SAMPLE INFORMED CONSENT FOR ANGIOGRAPHY

Table 6

Source: Compiled by Author

Angiography is a sterile operative procedure, with the room set up and the staff dressed in surgical attire (as in the operating suite). Preparation takes time because meticulous care is taken to be certain no air bubbles are present in injector systems, tubings, and catheters. Most angiograms are performed through arterial punctures, and air can be deadly in the arterial circulation. There are almost always some small air bubbles present in intravenous tubings, but this cannot be allowed during arteriography. Venous studies (e.g., a catheter placed in the femoral vein threaded up and through the heart to assess the subclavian vein) have their own potential dangers.

Femoral artery punctures are the usual arteriographic approach. Other approaches are the brachial or axillary artery and the translumbar approach, but these are used less often and only under specific circumstances. The common femoral artery is easily accessible, is fairly large, and has the lowest statistical complication rate (less than 0.5%) compared with translumbar (0.6%) and axillary (1.7%) approaches [77,78]. While the rates of major bleeding with femoral access have declined significantly over time, the transradial approach offers advantages of reduced vascular complications and length of stay and enhanced patient comfort and patient preference, while maintaining procedural success [79,80]. Moderate sedation is administered, and the radiologist finds the point of entry by palpating the femoral pulse. Local anesthetic is infiltrated subcutaneously, and the appropriate needle is used to catheterize the vessel.

When a hollow needle enters an artery, an immediate spurt of bright red blood results. Arterial bleeding is quite easy to differentiate from venous bleeding, both by the color of the blood and by the fact that it pumps rather than drips from the lumen of the needle. After cannulation of the vessel is accomplished, a guide wire is introduced. By means of fluoroscopic guidance, the catheter is inserted into the vessel over the guide wire. Unlike most other divisions of radiology, the interventional team should remain in the room with the patient during the entire procedure. Protective gear, such as lead aprons, thyroid shields, and eyeglasses, are worn at all times to protect the staff. A radiation dosimeter should be worn by all personnel involved in the angiographic procedure.

Arterial puncture site complications are rare and include thrombosis, arterial dissection, arteriovenous fistula, pseudoaneurysm, and hematoma, the last of which is most common [77,78]. Blood flow can be compromised during the procedure, resulting in ischemia, permanent organ damage, or death. As with any procedure, the benefit should be weighed against the potential risk of complications. While angiography in the hands of a qualified team is considered an extremely safe and advantageous procedure, no hospital should perform the procedure unless there is vascular surgery backup available should problems arise [81].

For decades, angiography has been an invaluable diagnostic tool for clinicians. The therapeutic applications of angiography have expanded greatly, with techniques including balloon angioplasty, femoral angioplasty, renal angioplasty, aortic angioplasty, and dialysis fistula and graft repair.

According to the American College of Cardiology, the American Heart Association, and the Society for Cardiovascular Angiography and Interventions, percutaneous revascularization is a reasonable option to improve survival, compared with medical therapy, in selected patients with low-to-medium anatomic complexity of coronary artery disease and left main disease that is equally suitable for surgical or percutaneous revascularization.

(https://www.jacc.org/doi/10.1016/j.jacc.2021.09.006 Last Accessed: June 1, 2022)

Level of Evidence: Expert Opinion/Consensus Statement

Balloon angioplasty, also known as percutaneous coronary intervention (PCI), is a nonsurgical means to open blood vessels blocked by atherosclerosis or other causes. The procedure is performed following diagnosis of the blockage by angiography.

The principles of angioplasty in any vessel are basically the same. The procedure consists of guiding a balloon-tipped catheter into the narrowed vessel under fluoroscopic guidance and inflating the balloon, which breaks the atherosclerotic plaque, presses it back against the walls of the vessel, and opens the narrowed segment. PCI is most commonly performed in the arteries of the heart and legs, but also may be performed in the vessels of the arms, kidneys, or abdominal organs. Angioplasty may also be of benefit in opening areas of surgical grafts that have begun to stenose.

Stenosed arteries can cause many types of problems. In the legs, they can lead to symptoms of pain with exercise (intermittent claudication) or even gangrene. In the kidneys, they may produce high blood pressure and/or poor renal function. Abdominal pain may result from decreased blood supply to various organs.

PCI may be performed instead of surgical bypass grafting, but each case should be individually evaluated and diagnosed. Inflating and deflating the balloon several times along the area to be dilated enlarges the vessel lumen by disrupting the plaque and intima in a controlled manner. When arteriosclerotic disease involves extensive segments of blood vessels, balloon angioplasty may not be feasible as it may be impossible to open large areas of a vessel with the standard equipment.

Certain drugs may be used before and at the time of balloon angioplasty. When there is a tight stenosis or stricture, it often becomes difficult to pass the wire through the narrowed portion of the vessel. The physician performing the procedure may ask the nurse to administer sublingual nifedipine, which results in vasodilatation and reversal of vasospasm when absorbed under the tongue. This may open the blood vessel just enough to allow passage of the wire and catheter. A small dose of intra-arterial nitroglycerine, administered directly into the artery by the physician at the point of the stenosis, will usually work along with the nifedipine to open the vessel. Tolazoline hydrochloride may be administered into the artery at the point of the vasospasm and usually opens the vessel enough to allow the stricture to be bypassed. As with any vasodilator, the staff should watch carefully for a drop in blood pressure and be ready to institute any measures necessary to maintain a steady pressure. Intra-arterial or intravenous heparin may be given as a bolus dose as the stenosis is crossed, both for its anticoagulant and antispasmodic effects.

While PCI is a safe and effective treatment for short vascular stenoses and occlusions, it is not without a small risk of potential problems, including reaction to the intravascular contrast media, a chance of renal failure, or vascular injury related to the catheterization itself and direct trauma caused by the balloon. Balloon angioplasty also gives a greater chance of acute arterial dissection, thrombosis, or distal embolization by the directed focal trauma it induces, as well as by the larger hole required at the percutaneous entry site. Rarely, the dilated artery may even rupture. There is also the potential for some of the arteriosclerotic plaque or small blood clots to break away and cause obstruction of blood flow farther along the path of flow through the vessel.

It should also be noted that vessels opened by PCI may begin to restenose. Repeat procedures may be indicated after a certain period of time, but the advantages of the procedure are potentially great [82,83,84].

Until recently, the standard treatment options for uterine fibroids have been myomectomy or hysterectomy, the definitive cure. However, surgery is not an option for many women, so they continue to bleed heavily during their monthly cycle.

Interventional radiologists have pioneered the use of uterine artery embolization as a treatment for symptomatic uterine fibroids. By occluding flow in the right and left uterine arteries, the fibroids are deprived of their blood supply. This leads to necrosis, degeneration, and eventual infarction of the fibroid, which results in a dramatic decrease in abnormal uterine bleeding and bulk-related symptoms [107].

Under moderate sedation and local anesthesia, the right or left femoral artery is punctured and catheters are guided into both uterine arteries. The uterine arteries are embolized with tiny polyvinyl alcohol particles, a fixative, and then a final angiogram is performed to confirm that there is no longer blood flow in the uterine arteries. Patients who undergo this procedure may experience cramping and are prophylactically medicated for this.

There have been studies and reviews to determine whether bilateral embolization is always necessary if fibroids are limited to one side of the uterus and are supplied by only one uterine artery. Some consider unilateral embolization to be effective, producing less postoperative pain and providing a greater margin of safety [108]. Other researchers point to the greater incidence of further interventions required, including hysterectomy, after unilateral embolization as proof that bilateral embolization should be standard practice in all cases [109].

A Cochrane review (that did not address unilateral versus bilateral embolization) did find that overall patient satisfaction was similar between embolization and hysterectomy or myomectomy and that embolization resulted in a shorter hospital stay and a faster return to routine activities. However, embolization was associated with a higher rate of minor complications and an increased likelihood of requiring surgical intervention within two to five years of the initial procedure [110].

Women should understand that it will take several months until the fibroid size decreases and results are realized. In addition, infertility may be a problem for some women undergoing this procedure because embolization significantly reduces the amount of blood available to the uterus during pregnancy. Restoration of uterine anatomy and ovarian protection have been identified as main predictive factors of obstetrical success [111]. Patient education is vital before any patient undergoes uterine artery embolization.

The potential of recombinant tissue plasminogen activator (rt-PA), or "clot buster" drugs, is well documented. The public is taught the importance of getting people who experience chest pain or stroke symptoms to a hospital emergency room as soon as possible. An arsenal of drugs is available in emergency rooms and chest pain centers that, when given in time, can save tissues from permanent damage by dissolving clots and restoring circulation. This type of therapy can be used to lyse blood clots that obstruct blood vessels elsewhere in the body, such as the lungs and limbs.

One rt-PA used for the management of arterial occlusions is alteplase, an enzyme that enhances the conversion of plasminogen to plasmin, which initiates local fibrinolysis with limited systemic proteolysis. Other thrombolytic agents that have been used include streptokinase (the first medication for myocardial infarction, introduced in 1958), urokinase (more widely used in the past), reteplase, tenecteplase, and anistreplase. The American College of Chest Physicians published a study in 2004 in which they compared most of these agents for their use in treating patients with acute myocardial infarction. For patients with symptom duration of more than six hours, alteplase is recommended over streptokinase [142]. In the same year, an evidence-based report stated that an IV rt-PA given within six hours of suggested stroke symptoms could provide beneficial results, including fewer long-term deaths and less dependence in the activities of daily living, despite the increase in initial fatalities [143]. The conclusions stated in this report were reaffirmed in 2009 [144]. The 6-hour timeframe has since been revised, and rt-PA has been found to be highly effective if administered within 3 to 4.5 hours [145,146,147,148]. However, there are limitations regarding patient selection. Administration of rt-PA is contraindicated in individuals with a systolic blood pressure greater than 185 mm Hg or a diastolic blood pressure greater than 110 mm Hg [145,146,148].

It should be noted that the risk/benefit ratio becomes unfavorable when alteplase is administered more than three hours after acute ischemic stroke; therefore, if the onset of stroke symptoms is greater than three hours or is unknown, treatment with this agent is generally not recommended [20,145,149]. The primary risk of alteplase treatment is intracerebral hemorrhage, and there are many contraindications for alteplase, including history of intracerebral hemorrhage, recent previous stroke (within three months), recent head injury, recent surgery, uncontrolled hypertension, seizures, active internal bleeding, or rapidly improving or minor stroke symptoms [146,148,149]. Despite the conventional 3-hour efficacy and safety window, the third European Cooperative Acute Stroke Study (ECASS III) has shown that, although it is optimal to begin treatment as early as possible, there are still modest benefits gained 3 to 4.5 hours after onset of a stroke if presentation is delayed [146,148,150]. While there was an increased incidence of intracerebral hemorrhage in the 3 to 4.5 hour ECASS III treatment (versus placebo) groups, the hemorrhage rate was no greater than current 3-hour treatment statistics; mortality was also not greater [150]. Other research supports extending the approved treatment window to 4.5 hours, but likewise, stresses the importance of beginning treatment as early as possible [146,148,151,152,153].

The novel drug desmoteplase, a recombinant form of the plasminogen activator DSPAα1, derived from the saliva of the common vampire bat, Desmodus rotundus, is being investigated in clinical trials for IV treatment of acute ischemic stroke in the 3- to 9-hour window. While results of initial safety trials (Desmoteplase in Acute Ischemic Stroke [DIAS]; Dose Escalation of Desmoteplase for Acute Ischemic Stroke [DEDAS]) showed positive results up to nine hours after the onset of symptoms, the DIAS-2 phase III trial was unable to show any benefit after three hours, although this was possibly attributable to poor trial design [152]. The DIAS-3 and DIAS-4 trials are underway to prove benefit up to the 9-hour mark despite the indication that tissue damage is likely permanent after 4.5 to 5 hours [152]. Recruitment into the DIAS-4 trial was ended prematurely due to disappointing results from DIAS-3; the manufacturer subsequently discontinued its development for use in ischemic stroke [154; 155; 156].

Intra-arterial rt-PA can be used as a thrombolytic agent following angiographic demonstration of intravascular thrombi. Because of the extreme potency of this agent, there are many contraindications for its use. Even though it is infused through a catheter that is angiographically placed at the site of the thrombus, it may be systemically absorbed. Because there is a real potential for bleeding, patients who receive this drug should be thoroughly screened. Most often this is completed by means of a checklist (Table 8).

INTERVENTIONAL RADIOLOGY THROMBOLYTIC THERAPY CONTRAINDICATIONS CHECKLIST

Table 8

Source: Compiled by Author

Newly formed blood clots are more susceptible to lysis, and as noted, there is some evidence that clots or emboli less than three to six hours old are more likely to dissolve with directed infusion than older lesions. Therefore, patients who present with sudden onset of pain and coolness in an extremity may be candidates for thrombolytic therapy.

Patients receiving intra-arterial thrombolytic therapy should be in an intensive care unit. Blood work should be monitored closely, with specific attention to the CBC, PT/INR, PTT, and fibrinogen levels. It is imperative to note any signs of systemic bleeding, such as hypotension and confusion. Extreme care should be taken with the arterial line. The catheter should remain taped securely in place. The drug infuses at the exact clot location, so the catheter should never be allowed to move.

Intramuscular injections or other procedures that may induce bleeding should be avoided during thrombolytic therapy administration. The drug is delivered by means of an infusion pump, and during the time of administration, patients should be continuously assessed for any signs of bleeding. The drug may be infused for six hours or longer, during which time the patient may be taken to the interventional radiology department for serial angiograms to assess the status of the dissolving clot. When the catheter is removed, special attention should be given to the puncture site and extra time for holding pressure on the site should be allowed.

With successful thrombolytic therapy, patients may be spared surgical procedures and prolonged hospitalization. Blocked arteries in the lower extremities, occluded surgical bypass grafts, dialysis access grafts, central venous occlusion, and acute upper extremity ischemia all have been helped by this form of therapy.

The superior and inferior mesenteric arteries supply blood to the small and large intestines. A disruption in blood supply in either of these arteries can lead to a variety of symptoms, including severe pain, nausea, vomiting, and diarrhea. The resulting acute mesenteric ischemia has a very high mortality rate. In certain patients, intense mesenteric vasoconstriction may occur without an obvious lesion. These are the patients who may develop mesenteric ischemia or infarction without vascular occlusion. In other words, the vessels are not obstructed by strictures or blood clots; they simply remain constricted. In cases such as these, the intra-arterial administration of papaverine hydrochloride may be lifesaving.

Papaverine, a hydrochloride of an opium alkaloid, relaxes various smooth muscles, especially those of the larger arteries. This relaxation may be pronounced, especially if spasm exists. Relaxation is noted in the vascular system and bronchial musculature and in the gastrointestinal, biliary, and urinary tracts. The antispasmodic effect is direct and is unrelated to muscle innervation.

The indication for papaverine hydrochloride therapy is confirmed at the time of the diagnostic angiogram as many other conditions can mimic these symptoms. Patients who experience acute mesenteric ischemia are quite ill and may already be receiving moderately high doses of analgesics for intense abdominal pain; consequently, IV moderate sedation for the angiogram may not be needed. In some cases, a test injection of tolazoline hydrochloride will be given directly into the affected artery to test for vasodilation activity. If the response is good, the decision may be made to institute papaverine therapy.

Papaverine hydrochloride is given via continuous pump infusion directly into the involved artery. It has an explicit relaxant effect on smooth muscle, particularly muscles in spasm. The half-life of papaverine hydrochloride is 30 minutes to two hours, so patients receiving this drug should be watched very carefully [20]. They should be taken directly from the interventional radiology suite to the intensive care unit, where the staff should be certain that the catheter is not moved from its predetermined secured site.

The most important side effect of papaverine is hypotension, as the vasodilation produced by the drug may cause a significant decrease in blood pressure. A patent intravenous line is essential to provide access for fluid administration. The only direct contraindication for papaverine is heart block, which can further increase conduction delays. The drug also should be used with extreme caution in patients with acute angle glaucoma. Abdominal pain and diarrhea during mesenteric infusion are common and may reflect successful reperfusion rather than the development of bowel infarction [20].

According to the American College of Radiology, the use of a microcatheter allows for distal access and superselective embolization of single vasa recta at the site of bleeding. Instead of embolic material, vasopressin infusion is indicated when a diffuse source of bleeding is identified or when superselective catheterization fails or is not technically possible.

(https://acsearch.acr.org/docs/69457/Narrative Last Accessed: June 1, 2022)

Level of Evidence: Expert Opinion/Consensus Statement

Vasopressin causes contraction of the smooth muscle of the gastrointestinal tract. Vasopressin injection has been administered IV or intra-arterially into the superior mesenteric artery as an adjunct in the treatment of acute, massive gastrointestinal hemorrhage caused by ruptured esophageal varices, peptic ulcer disease, esophagogastritis, esophageal laceration, acute gastritis, colitis associated with Behçet syndrome, small intestinal typhoid infection, Mallory-Weiss syndrome, or intestinal perforation. Use of vasopressin in such situations is a temporary measure, intended to decrease portal venous pressure and increase clotting and hemostasis. With the advent of super-selective embolization, vasopressin is reserved for cases in which embolization would result in excessive occlusion [157].

Emergency colon surgery can be risky, and the administration of this drug can stop bleeding permanently or delay future episodes of hemorrhage until the patient is stable enough to undergo elective surgery. Once a bleeding point is established by angiographic examination, the infusion catheter is positioned in either the superior or inferior mesenteric artery and drug administration is begun by means of an infusion pump. Dosages may be titrated accordingly to control the bleeding.

Vasopressin should be used with extreme caution in patients with coronary artery disease because the vasoconstrictive effects may systematically result in constriction of the coronary arteries [20]. In such patients, even small doses may precipitate anginal pain. With larger doses, the possibility of myocardial infarction should be considered.

Vasopressin may also produce water intoxication, so early signs of drowsiness, listlessness, and headaches should be recognized to prevent serious effects [20]. The patient receiving intra-arterial vasopressin should be in an intensive care unit where any signs of angina may be observed. The staff should carefully monitor urinary output and observe for abdominal cramping and change in stool color.

Vasopressin should never be stopped suddenly. It is extremely important to taper the dosage when stopping intra-arterial administration of the drug.

Interventional radiology is primarily concerned with treating existing morbidities, with the main exception of angiography, and adverse effects of guided imaging are generally considered acceptable risks because they are comparably less important than life-saving procedures or vast improvements in quality of life. Nonetheless, it should be remembered that the ALARA protocol recognizes that no level of radiation is known to be completely safe, and a conscious effort should be made by all healthcare professionals to use diagnostic and follow-up imaging sparingly [159].

In 2020, CT scans were performed at the rate of more than 220 per 1,000 Americans [160]. It has been estimated that in the next few decades nearly 30,000 cancers will be caused by exposure to this radiation. Others feel this is an overestimate and that the risk of cancer is actually reduced by having CT scans (at least for adults) due to a process called radiation activated natural protection, whereby small doses of intense radiation kill precancerous cells and provide immunity against future cancers [161]. In either case, imaging statistics have revealed trends of unnecessary procedures, duplicate testing, and physician self-referral, causing more than $26 billion in excess healthcare expenditures and a corresponding increase in health insurance cost [162,163]. There are many factors that may be contributing to these trends, including the increase in available technology and physicians trained to use it, a rise in the practice of defensive medicine, and the use of physician-induced care. However, the fact remains that millions of radiologic tests will be performed each year, of which 20% to 50% are redundant or not beneficial to patients' diagnosis and treatment [164,165]. Various studies have found [166,167,168,169,170]:

From a purely economic standpoint, this kind of waste can be considered a moral hazard. In many cases, the negative repercussions of imaging overuse are passed on to the patient, while the facility and physicians experience no downside. Additionally, ordering many tests is considered by some to be an effective risk management strategy. However, there is a substantial gap between physicians' perceived risk of malpractice and their actual risk, with physicians perceiving a much greater risk of malpractice than has been documented for their specialty [171,172]. For example, in a survey of neurologists, respondents estimated that 8 per 100 neurologists in their state would be sued within the following year; this compared with American Medical Association data that indicated a risk of 1.49 per 100 [173,174]. Similarly, radiologists have estimated their risk of litigation within five years as 35%, which compares with an actual rate of approximately 10% [171].

Balancing the benefits and risks to patients, the risks of litigation, and, possibly, the burden on the healthcare system can be challenging. It is important to reflect on this balance from time to time in order to ensure that patients continue to receive safe and effective care.

While the vast majority of patients who undergo short-stay radiologic procedures do very well, complications can and do occur. It is important to always discuss the possible complications when explaining procedures to patients before the informed consent form is completed. A nurse can serve as a resource person to clarify and reinforce key points and help assess how well the patient and family members comprehend the upcoming procedure and its possible and anticipated outcomes.

Communication with patients regarding interventional procedures and expectations is a vital aspect of promoting positive outcomes. An interpreter should be acquired if the patient is more comfortable communicating in another language. Frequently, this may be easier said than done, as there may be institutional and/or patient barriers. In the multicultural landscape, interpreters are a valuable resource to help bridge the communication and cultural gaps between patients and practitioners. Interpreters are more than passive agents who translate and transmit information back and forth from party to party. When they are enlisted and treated as part of the interdisciplinary clinical team, interpreters serve as cultural brokers, who ultimately enhance the clinical encounter. When providing care for patients for whom English is a second language, the presentation of education materials in the individual's native language may improve understanding and outcomes.

It is during instruction that patients usually hear that the benefits of the procedure greatly outweigh any possible risks. In certain instances, however, risks become greater, and in those cases, patients and their families should be aware of what sequelae could result. All these procedures are, by definition, invasive, and invasive procedures interfere with the natural defenses of the body.

In some hospitals and imaging centers, signed consent is obtained before patients receive intravenous x-ray dye for a basic CT scan or dye injection. Whether this protocol is in effect, it is important that patients understand why the contrast is being given, how it works, and what feelings and sensations they may experience during its administration. Contrast materials are usually given by a power injector, with a bolus injection of up to 150 cc into the vein at a flow rate of 2–4 cc per second.

CT contrast materials usually have an iodine base, but even nonionic agents have a potential for reactions. The nonionic dyes are less likely to cause electrical interference in the heart, cerebral symptoms, hives, itching, nausea, or vomiting. However, patients still have the potential to respond adversely as the dye rapidly mixes with the circulating blood volume. Mild reactions are not unusual. Many patients experience a warm or hot flush or a metallic taste that disappears within one to two minutes. Hopefully, any patient who has previously reacted to iodinated contrast medium should know about this reaction.

As with any allergy, a person should be aware that this drug may present a potentially life-threatening problem in the future. Convulsions, pulmonary edema, hypotensive shock, and cardiorespiratory arrest are possible life-threatening reactions. It is vital to advise the person who has a reaction that he or she is allergic to the contrast medium and inform other healthcare personnel of this should any future studies requiring contrast agents be considered. In this way, the pros and cons of contrast administration may be properly evaluated. Premedication may be necessary or contrast materials may need to be totally withheld. An MRI, ultrasound, or nuclear medicine examination may offer similar yet safer results for a patient who has had an allergic reaction to a contrast agent in the past.

It should be noted that the radiology staff has a responsibility to communicate with all of the patient's caregivers if a patient has a problem with the contrast medium. A complete report should be given so that the floor or short-stay staff is aware of the reason the patient returns with hives or comes back sleepy from a diphenhydramine injection.

IV moderate sedation is another area that the staff may take for granted. Although there are a few patients who ask to be awake so that they can watch the procedures on the video screen, most patients prefer to sleep through the procedure. It is important to make patients and their family members aware that IV moderate sedation is not general anesthesia and it is given to relax the patient just enough to assure that he or she is as comfortable as possible. Staff members who are familiar with moderate sedation often hear patients tell them that they are still awake and need more medicine to go to sleep. Patient teaching should include the fact that small doses are given as needed and patients do not have to be sound asleep for these types of procedures. In fact, many procedures require that patients cooperate with breath holding and not moving a certain body part.

It is possible that the respiratory depressant effects of moderate sedation may last longer in certain patients, which is one reason that patients should be closely observed in the same-day surgical area or on the medical-surgical floor for several hours. The radiology staff's responsibility for teaching extends to all members of the medical staff who will be in contact with these patients during the postprocedure hours. Respiratory depression, hypotension, nausea, and vomiting are serious potential side effects from the use of IV moderate sedation.

Before patients are discharged, they should be assessed for stability of vital signs, return of all reflexes, satisfactory airway, complete motor control, and alertness or a return to the preprocedure level of consciousness. Instructions should be both verbal and written and should stress the importance of avoiding alcohol intake, driving, or operating heavy machinery until the following day.

All procedures present some degree of risk. Unlike open surgery, in which an organ or tissue is sampled directly, interventional radiologic procedures use guidance systems to provide indirect visualization of the organ systems. With conventional surgery, bleeding sites and perforations may be plainly noted, but this is not the case with transcutaneous procedures. Complications do happen, and patients, families, and healthcare workers should be aware of their potential.

All those involved should be aware of the normal reactions and what may be indicative of more serious problems. Any time a puncture is made into living tissue, there is some bleeding to be expected. That is the basic reason that direct pressure is applied to a venipuncture site. When a puncture is made or a piece of tissue is sampled by means of a long needle, however, no such direct pressure can be exerted. Therefore, it is normal for some bleeding to occur, and that concept should be made clear. The trick is to be able to discern when there is a real problem.

Any blood, even just a few drops, that leaks onto the peritoneum causes irritation and pain. If the site is near the diaphragm, the blood may cause irritation to the diaphragm or phrenic nerve and the patient may have some referred shoulder pain, hiccoughing, or pain with deep breathing. All pain, however, is subjective, and what one patient may consider to be excruciating, another may barely notice. This is why all patients should be observed closely for classic signs of hemorrhage and dyspnea for several hours before they are sent home. The written instructions should be reinforced at this time by the discharging nurse, who should be certain that patients and their caregiver(s) know what to do if they feel there is an exacerbation in or new onset of any postoperative symptoms.Table 9 is an example of an instruction form that can be sent home with the patient.

SAMPLE CT SCANNING DEPARTMENT OUTPATIENT BIOPSY POSTPROCEDURE INSTRUCTIONS

Table 9

Source: Compiled by Author

Certain procedures carry their own risks. A lung biopsy patient should be made aware of the importance of calling for assistance if he or she should experience sudden difficulty breathing. This is not to be compared to soreness at the surgical site or the immediate postprocedure discomfort with deep breathing.

Patients who have undergone pancreatic or hepatic procedures have a slight but real chance of developing pancreatitis or a small bile leak. These patients should be informed that fever, vomiting, chills, and increased pain are danger signs that may indicate an acute abdomen. This is a complication that may result from any abdominal procedure, including celiac plexus blocks, transhepatic cholangiograms, cyst drainages, TIPS, and various biopsy procedures.

Angiography and angioplasty patients should be fully aware of the real potential for postprocedure bleeding. While some facilities use sandbags over arterial puncture sites, others do not. There is a possibility that if the femoral artery leaks, it can quickly pump quite a bit of blood into the compressing sandbag before the hemorrhage is discovered. Patients and short-stay procedure staff should be told of the importance of keeping the leg straight and relatively immobile for several hours after the procedure. It is not at all rare for a site to begin bleeding again when motion or ambulation is started too early. Before discharge, the written instructions should be verbally reinforced, along with a demonstration of how to apply pressure if bleeding does occur. Most angiography patients experience some type of ecchymosis or even a small hematoma at their puncture sites. Education should include the signs of significant bleeding into the tissue around the groin, as some hemorrhages can be internal rather than overt.

A cool leg with a change in color may signify a problem with a blood clot. Pain, the most common sign of embolus, is obvious to the patient, but all involved should be taught the importance of direct visualization of both extremities after an angiogram or angioplasty. Both staff and caregivers should remember that most often a puncture in the right side of the groin means that the repair of the vessel has been performed on the opposite side. Therefore, pain and discoloration of the left leg should not be ignored simply because the puncture is on the right side.

A swollen arm after a subclavian stent insertion should not be taken lightly. Strictures may form and clots may develop in and around these areas, which lead to compromised circulation. Patients should be aware that an arm that gradually increases in size may signal a significant problem.

The importance of educating patients, home caregivers, and staff cannot be overstressed. While the benefits of short-stay procedures overwhelmingly surpass older techniques of open surgery with corresponding long hospitalizations, it is necessary to anticipate the complications that may occur. Simply saying that problems may happen is not enough. Nurses' role as teachers should be realized, and education of patients and staff should be a high priority.