Interventional Radiology: An Overview

Symposium on Radiology

Interventional Radiology An Overview

Klemens H. Barth, M.D., * and M ichael A. M ertens, M.D. t

The term "interventional radiology" applies to a variety of invasive radiologic procedures now commonly performed by radiologists with special experience in catheterization techniques. The term was coined by Margulis in 196729 in an effort to group all invasive radiologic techniques guided by x-ray or ultrasound (Table 1). With few exceptions such as aspiration biopsy and blood sampling techniques, interventional radiology procedures are primarily therapeutic and would probably best be addressed as "therapeutic radiology" had this term not already been reserved for radiation therapy. Several breakthrough developments in instrumentation have contributed to considerable growth in interventional radiology. The introduction of the minimally traumatic thin-caliber Chiba needle has not only rekindled interest in transhepatic cholangiography but paved the way for transhepatic biliary drainage, access to the portal venous system for venous blood sampling, and embolization of esophageal varices.l8 , 19,34 Such "fine needles" (20 to 22 gauge) also allow low-risk aspiration biopsies. Catheterguided embolotherapy was first applied to gastrointestinal (GI) bleeding, which arterial vasopressin infusion had failed. to control. Introduction of a variety of embolic materials such as the "coil-spring embolus" and flowdirected detachable balloons expanded applications of embolotherapy. Not only has the angiographic catheter become a tool for therapeutic uses in blood vessels but it can also be used for nonvascular applications such as drainage of bile, urine, and intra-abdominal fluid collections. Finally, an ingenious catheter modification inaugurated by Porstmann, the so-called "caged balloon," allowed expansion of a catheter-mounted balloon to a predetermined diameter. 39, 40 Using a different plastic material, Gruntzig and co-workers introduced the limited expansion balloon catheter now most widely used for so-called "transluminal angioplasty."23 Development of the sono graphic biopsy transducer brought organs such as the pancreas, the liver, and the kidneys into reach of visually *Professor of Radiology, and Director, Division of Angiography and Interventional Radiology, Georgetown University Hospital, Washington, D.C. tAssistant Professor of Radiology, Georgetown University Hospital, Washington, D.C.

Medical Clincs of North America-Vo!' 68, No. 6, November 1984

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Table 1.

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Interventional Radiology Procedures

DIAGNOSTIC

THERAPEUTIC

Percutaneous needle biopsy under fluoroscopic--CT-ultrasound guidance Percutaneous venous sampling for hormonally active tumors (parathyroid, adrenal, ovarian, pancreatic) Renal cyst puncture Antegrade pyelography

Arterial vasopressin infusion for control of upper and lower Gl bleeding Embolotherapy for spontaneous, posttraumatic, tumor-induced bleeding Embolic ablation of spleen, kidneys, parathyroid glands Embolotherapy for palliative ablation of nonresectable tumors Embolotherapy for vascular malformation and arteriovenous fistulae Percutaneous placement of long-term arterial infusion catheters with rerouting of blood flow by embolization Percutaneous retrieval of intravascular foreign bodies Percutaneous transluminal angioplasty of stenoses and occluded vascular segments Percutaneous pulmonary valve dilatation Percutaneous dilatation of biliary, urinary, and esophageal strictures Regional infusion of thrombolytic agents Regional infusion of vasodilators for mesenteric and peripheral vascular vasospastic disease Percutaneous nephrostomy, ureter stenting Percutaneous renal stone extraction Percutaneous abscess and fluid drainage

guided needle entry. Using the percutaneous catheterization principle developed by Seldinger, the way was opened for, sonographically guided catheter placement for drainage of deep-seated abscesses and fluid collections. Recently introduced percutaneous transluminal extraction of renal pelvic or ureteric stones proves that there is no fundamental barrier between entering the kidney with a 22-gauge needle and widening this tract within minutes to 10 times the needle diameter, allowing percutaneous introduction of endoscopes and retrieval instruments.1O Most of these techniques owe their existence to diagnostic angiographers familiar with remote guidance of needles and catheters. From among the numerous interventional radiology procedures whose detailed description has already filled textbooks, we shall discuss those of particular interest to the readership, emphasizing indications and risks, as well as immediate and long-term effects as applicable. 2, 26, 45

NEEDLE ASPIRATION BIOPSY Several factors are essential to the safety and diagnostic accuracy of this minimally invasive diagnostic technique. Use of fine needles (20 to 22 gauge) reduces the risk of hemorrhage, pneumothorax, or fluid leakage. Most aspiration biopsies can be performed on outpatients. The exception

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is lung biopsies in patients with known obstructive pulmonary disease because of their intolerance to even a small (10 to 20 per cent) pneumothorax. Proper needle technique by the radiologist, adequacy of processing the aspirate, and the pathologist's familiarity with cytopathologic diagnosis are keys to success of fine-needle aspiration biopsy (Figs. 1 to 4). In order to maximize diagnostic efficiency, the needle aspirate should be processed in three different ways. Part of the material should be immediately spread on glass slides and fixed in 95 per cent alcohol. A second part should be immersed in a pH balanced solution and filtered before being spread on slides, fixed, and stained. Another part of the suspension should be centrifuged and the cell block treated similar to a histologic specimen. If a small fragment of tissue can be obtained, it should be subjected to routine histologic processing. If the lesion to be biopsied is potentially inflammatory, part of the aspirate should be used for Gram stains, acid-fast stains, or fungal stains and another part placed directly into culture media. Three or four needle aspirations generally suffice. Cytopathologic diagnosis is based on nuclear morphology, which is distinct in most carcinomas. Benign tumors, lymphomas, and inflammation are better characterized by tissue analysis; therefore, an effort needs to be made to obtain histologic specimens for which 22-gauge needles with a cutting edge are available. Twenty-gauge needles are better suited for core biopsy. As with many other clinical procedures, needle aspiration biopsy is most productive if the referring physician discusses the clinical question carefully with the radiologist including specific risks for the patient under consideration. The radiologist in turn needs to communicate with the pathologist the type of biopsy he or she intends to perform, whether or not

A Figure 1. Pulmonary aspiration biopsy of metastatic carcinoma of pancreas. A, Initial chest radiograph showing nodule in left lower lobe. B, A 20-gauge aspiration needle positioned close to the nodule. The nodule is superimposed over the pulmonary hilum (arrow). The needle is redirected into the periphery of the nodule under biplane fluoroscopy.

B

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Figure 2. eT-guided liver biopsy of metastatic small cell carcinoma. A 22-gauge needle is advanced into the metastatic lesion in the posterior portion of the right lobe, well demarcated from normal liver by its low attenuation.

bacteriologic specimens are to be obtained, and if quick stains are necessary to determine adequacy of the aspirated material before the patient leaves the biopsy table. If such efforts are made the number of false-negative or equivocal aspiration biopsies can be significantly reduced. CONTROL OF GASTROINTESTINAL BLEEDING

We shall discuss the majority of spontaneous upper and lower gastrointestinal bleeding in these categories: 1. Upper gastrointestinal (Cl) bleeding: bleeding varices, hemorrhagic gastritis, stress ulcerations, bleeding gastric and duodenal ulcers. . 2. Lower Cl bleeding: bleeding diverticula, angiodysplasia and arteriovenous malformations. 3. Miscellaneous bleeding sites: hematobilia, bleeding pancreatic pseudocysts, mycotic aneurysms, Crohn's disease, stomal bleeding. Rapid blood loss characterizes most acute Cl bleeders and requires emergency treatment. As soon as the patient is stabilized by volume support, diagnostic studies should be undertaken to direct definitive treatment. Hematemesis calls for upper endoscopy and all efforts should be made to clear the stomach of blood, to allow adequate visualization. Endoscopy is the preferred initial work-up since it establishes both the site and the cause of bleeding. Angiography can usually only determine the site of bleeding. Cl bleeders with bright red blood per rectum should first undergo rectosigmoidoscopy. If no bleeding site is identified, diagnostic angiography is the next step. Since Cl bleeding tends to be intermittent, the arteriogram may be negative in a patient who has recently passed a large amount of blood rectally. Sometimes repeat arteriography is able to demonstrate a bleeding site owing to the vasodilatory effect of contrast material. For the same reason, vasodilator-augmented angiography appears

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Figure 3. Aspiration biopsy of cholangiocarcinoma (Klatzkin's tumor). A, Aspiration of the obstructing porta hepatis mass using a Greene needle under biplane fluoroscopy. B, Tandem technique can be used for needle placement if biplane fluoroscopy is not available. The position of the first needle is checked by lateral radiography. C, The second needle is guided alongside the first to predetermined depth under single-plane fluoroscopy.

Figure 4. Aspiration biopsy of carcinoma of the head of the pancreas under ultrasound guidance. Calibration lines indicating the required needle trajectory aid in needle direction. Strong needle tip echo by 22-gauge aspiration needle (arrow).

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appropriate in instances where demonstration of the bleeding site is crucial to management. In recent years radio nuclide studies using technetium-Iabeled red blood cells or sulfur colloid have emerged as screening tests for lower GI bleeding. 1. 14 These are particularly helpful in low-grade intermittent bleeders where arteriography fails to demonstrate extravasation. We find labeled red cells particularly helpful since they allow repeated imaging and a better chance for tracking intermittent bleeding. Positive scans may be taken as a basis for vasopressin infusion or even surgery if arteriography is unsuccessful. When the test is used for the choice between right or left hemicolectomy, one has to consider that activity extravasated from the right colon may have moved to the left colon by the time of imaging. Vasopressin infusion has now been used for many years either intravenously or intra-arterially to control gastrointestinal bleeding. 33 Laboratory animal studies demonstrate that doses equivalent to 0.2 units per minute in humans reduce gastrointestinal blood flow by about 50 per cent. A further increase in dose does not lower mesenteric flow proportionally; however, it significantly increases the risk of cardiovascular complications. Unless required by the development of coronary ischemia or hypertension, vasopressin should not be stopped abruptly but reduced gradually to prevent rebound vasodilatation with its potential for recurrent bleeding. Contraindications to vasopressin are well known and include ischemic heart disease, hypertension, renal failure, and ischemic peripheral vascular disease. Vasopressin infusion requires continuous electrocardiographic monitoring to discover ischemic effects as early as possible. UPPER GASTROINTESTINAL TRACT BLEEDING ,

Variceal Bleeding As an initial measure, intravenous vasopressin is infused at the rate of 0.2 to 0.4 units per minute. Patients in whom vasopressin fails or in whom it is contraindicated because of cardiovascular disease can be treated with percutaneous transhepatic embolization of esophageal varices. The latter procedure carries a 20 per cent risk of portal vein thrombosis. It is a temporizing measure to improve the patient's condition and render him or her a candidate for elective instead of emergency decompressive shunt operation. Erosive Gastritis and Stress Ulceration The incidence of erosive gastritis has been considerably reduced by administration of cimetidine and gastric suction in high-risk intensive care patients. If massive bleeding from such lesions occurs, vasopressin infused directly into gastric arteries is the treatment of choice (Fig. 5). Experience has shown that the intra-arterial route is preferable. Dosages should not exceed 0.3 units per minute. An important adjunct to vasopressin infusion for gastric bleeding is placement of a large-caliber soft rubber catheter with intermittent suction and lavage. A blood-filled distended stomach responds poorly to conservative treatment! If endoscopically diagnosed hemorrhagic gastritis does not respond to vasopressin and

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Figure 5. Vasopressin therapy of erosive gastritis. A, Selective left gastric arteriogram showing contrast extravasation along the lesser curvature. B, After 30 minutes of intravenous vasopressin therapy (0.2 U per minute), there is persistent extravasation. C, After identical time and dosage of vasopressin via left gastric artery infusion, there is marked vasoconstriction and cessation of bleeding. Note constriction of the splenic artery but not of the hepatic artery.

there is no obvious reason for failure, such as depletion of clotting factors, it may be best to again examine the patient endoscopically and look for a missed gastric or duodenal ulcer. It is well knbwn that ulcer bleeding responds poorly to vasopressin infusion. 54

Bleeding Ulcer A bleeding peptic ulcer is primarily an indication for surgical treatment both from the standpoint of hemostasis and for control of hyperacidity. In cases of high surgical risk, transcatheter embolization of the feeding left gastric or gastroduodenal artery has a 75 to 80 per cent chance of achieving effective hemostatis (Fig. 6). Failure of embolotherapy is mainly due to inability to reach the appropriate artery by catheter. In an intact gastric circulation, one of the major feeding arteries can be embolized safely.41 The most significant risk of embolotherapy is dislodgement of embolic material downstream into the aorta. Renal and mesenteric infarcts, as well as ischemia of the toes, have been reported. Careful attention to embolization technique can largely avoid such complications. Gastric and duodenal mucosal infarction following embolotherapy was reported in patients who had received vasopressin after embolotherapy. Therefore vasopressin should not be continued if the patient undergoes embolization.

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Figure 6. Embolization for bleeding duodenal ulcer. A, Celiac arteriogram showing no definitive evidence of bleeding in the duodenum. Large gastroduodenal artery is present (arrow). B, Selective gastroduodenal arteriogram showing extravasation into distended duodenal bulb (arrow). C, After embolization of the distal gastroduodenal artery bleeding is no longer evident.

LOWER GASTROINTESTINAL TRACT BLEEDING

Massive bleeding from sites in the small bowel is rare. We have seen bleeding from leukemic infiltrates, mucosal sloughing as a result of chemotherapy, and bleeding from a primary adenocarcinoma in the jejunum. In none of these instances did the bleeding respond to intra-arterial vasopressin. The most frequent sites of massive lower GI bleeding are right colon diverticula. Apparently because of anatomic differences in the wall of the right colon, these diverticula are much more likely to bleed than those in the left colon (Fig. 7). Diverticular bleeding responds well to intra-arterial superior mesenteric artery infusion of vasopressin. A main reason for failure is a clotting deficiency, which is always suspected in patients with massive blood transfusions. Therefore transfusion should be used only as an initial stabilizing measure. If the site of bleeding cannot be demonstrated with diagnostic angiography because of the intermittent nature of such bleeding, the angiographic catheter can be left within the superior mesenteric artery for up to 24 hours with continuous Hushing. This allows

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Figure 7. Vasopressin treatment for diverticular bleeding in the right colon. A, Extravasation of contrast medium in the region of the proximal ascending colon supplied by the ileocolic artery (arrow). B, After 30 minutes of vasopressin infusion (0.2 U per minute) into the superior mesenteric artery, there is generalized vasoconstriction and cessation of bleeding.

quick repeat angiography for localization, should bleeding recur. Alternatively, vasopressin infusion can be started without delay if recurrent bleeding is clinically evident. Use of embolotherapy in the distribution of the superior mesenteric artery is not recommended because the risk of mucosal infarction is considerable. However, successful embolization of branches of the superior mesenteric artery has been reported. Embolization should not extend beyond the mesenteric arcades since the straight arteries represent end arteries. Total cessation of blood flow to the bleeding site is not a prerequisite for successful control of bleeding. MISCELLANEOUS BLEEDING SITES

Bleeding from enterostomies responds well to infusion of vasopressin. Hemobilia, the triad of right upper quadrant pain, jaundice, and lower Cl bleeding, occurs most frequently as complication of bile duct surgery, liver biopsy, and transhepatic catheterization for percutaneous biliary drainage. Embolization of the lacerated hepatic artery has been curative and appears to be the procedure of choice. Bleeding from pancreatic pseudocysts has also been controlled by embolotherapy. Frequently, large arteries are involved in such bleeding and definitive occlusion of these arteries with nonresorbable emboli such as Ivalon particles, spring coils, or detachable balloons becomes necessary (Fig. 8). EMBOLOTHERAPY As previously mentioned, embolization of a bleeding gastric ulcer was among the first clinically performed therapeutic embolizations. 46 Present

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Figure 8. Embolization of post-splenectomy splenic artery stump erosion with fistula into the left colon presenting as lower Cl bleeding. A, Massive bleeding from splenic artery stump at origin of an omental branch. Vasopressin-induced constriction of splenic artery which did not affect the large artery bleeding. B, Following embolization of the distal splenic artery with Ivalon particles, there is cessation of bleeding and retrograde filling of the omental branch.

indications include spontaneous and post-traumatic bleeding as discussed in the previous section on gastrointestinal bleeding, and palliative, in situ ablation of vascular malformations and tumors. Selected indications for embolotherapy will be discussed. Renal Trauma Renal trauma can be quite effectively managed by selective embolization of the bleeding artery. Recurrent gross hematuria following needle biopsy should be investigated arteriographically to determine the source of bleeding and embolize the bleeding artery if feasible. A relatively infrequent source of spontaneous gross hematuria are'intrarenal arteriovenous malformations. These vascular lesions are typically located in the peripelvic region and can lead to massive intermittent blood loss. Angiography is the only reliable method of diagnosis (Fig. 9). Among the advantages over surgical treatment is maximal preservation of renal tissue. Embolization of the Spleen Therapeutic embolization of the spleen has become known as "medical splenectomy." It is palliative treatment for hypersplenism secondary to portal hypertension, pernicious anemia, spherocytic anemia, leukemia, and trauma. 35 The main risks of this procedure include abscess formation and sepsis which are related to the extent of the embolic infarction of the spleen. According to accumulated experience, no more than 60 per cent of the splenic parenchyma should be embolized at one time. 49 The end-point of splenic embolization is best determined by the effect on platelet survival and improvement of clotting status. Embolotherapy may be carried out in several stages to achieve a lasting clinical result. Strict aseptic technique is of the utmost importance during splenic embolization. Massive Hemoptysis Massive hemoptysis is defined as continued blood loss of more than 500 ml over 24 hours. Massive hemoptysis is seen in patients with cavitary

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A Figure 9. Embolotherapy of renal arteriovenous malformation (AVM). A, Small AVM in renal medulla causing several episodes of massive hematuria. B, After selective embolization of AVM with Ivalon particles. C, Post-embolization renal arteriogram with selective occlusion of the AVM and preserved normal renal arteries.

tuberculosis, aspergillomas complicating sarcoidosis, and chronic bronchiectases; among the latter are young adults with cystic fibrosis,l6, 52, 55 Rarely, massive hemoptysis is caused by a primary lung tumor such as adenocarcinoma or pulmonary arteriovenous malformation. Except for the rare tuberculosis-related "Rasmussen aneurysm"43 of a pulmonary artery or a pulmonary arteriovenous malformation, hemoptysis originates from bronchial arteries. Since bronchial artery embolization is relatively safe and effective, it should not be unnecessarily deferred. It is desirable to localize the lobar origin of the bleeding by bronchoscopy since bronchial arteriography is not likely to demonstrate extravasation. Because of the intermittent nature of the bleeding, bronchoscopy may fail to reveal active bleeding. 55 In these instances the clinical situation determines whether bronchial artery embolization should be carried out. Enlargement of bronchial arteries second-

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ary to chronic bronchiectasis aids in the selection of the arterial trunk to be embolized. 16,52 Resorbable embolic material such as Gelfoam is quite appropriate (Fig. 10).42 Repeat embolotherapy for recurrence is appropriate, particularly when large bronchial arteries are present which cannot be occluded safely in one session. The major risk of bronchial artery embolization is spinal cord ischemia from embolic occlusion of the branches to the spinal cord which may originate in about 10 per cent of cases from bronchial arteries, particularly on the right. It is the purpose of selective arteriography to demonstrate this potential spinal cord feeder branch prior to embolization. The presence of such an artery is a relative contraindication to embolotherapy. In lifethreatening hemoptysis, the risks of spinal cord ischemia, generally recognized as being less than 1 per cent of all bronchial artery embolizations, may be regarded as tolerable in comparison to life-threatening hem orrhage.28, 42, 52 Pulmonary Arteriovenous Malformations Pulmonary arteriovenous malformations can be embolized effectively with detachable balloons since the feeders are usually one to three pulmonary arteries that can be occluded individually.4 A particular challenge

Figure 10. Embolotherapy of massive h~moptysis in cystic fibrosis. A, Enlarged right costobronchial trunk supplying upper, middle, 'and lower lobes. Bleeding is suspected from upper lobe but is not demonstrated on arteriogram. B, After embolization with Gelfoam particles, there is occlusion of bronchial artery branches. The first intercostal artery, as well as the bronchial artery trunk, remains patent. Distal embolization is important to ensure lasting success of embolization.

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is patients with multiple pulmonary arteriovenous malformations in OslerWeber-Rendu disease. Embolotherapy in such instances attempts to occlude the largest shunts and is guided by blood gas analysis. If adequate oxygen saturation is achieved, the procedure may be terminated and further embolotherapy deferred until progres~ion of shunt formation requires further treatment. In our own experience such patients may undergo up to five embolization procedures. Pelvic Arteriovenous Malformations Pelvic arteriovenous malformations are nearly impossible to occlude by embolization because of the multitude of actual and potential feeding arteries (Fig. ll). Surgicalligation of the internal iliac arteries, usually the principal feeders, can only provide short-lived palliation and blocks the route for more selective embolization. 12, 36 In the presence of large shunts, embolotherapy may fail simply because of large caliber of the fistula, Embolization combined with operative dissection of pelvic arteriovenous malformations has been reported to improve results.l 2 Tumors Tumor embolization is being used prior to debulking of nonresectable tumors or to control tumor-related spontaneous bleeding. 3 Renal tumors have been those most frequently embolized (Fig. 12).3 Different from se-

Figure 11. Embolization of pelvic arteriovenous malformation (AVM). A, Initial arteriogram of right pelvic AVM with enlarged internal iliac artery as primary feeder. B, After embolization with Ivalon particles, subtotal occlusion of AVM. Recurrence is expected. Palliation can be achieved and embolization repeated as long as internal iliac artery trunk remains patent.

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Figure 12. Palliative embolization of bleeding metastatic renal cell carcinoma. A, Preembolization arteriogram showing large vascular tumor in right kidney. There is extension into the renal vein. B, After embolization with Ivalon particles and steel coils, there is occlusion of all intrarenal branches. Bleeding has stopped. The post-embolization syndrome lasted 3 days.

lective embolotherapy for benign arterial bleeding, the intent in tumor embolization is to occlude the entire blood supply to the tumor tissue. Therefore distal and permanent occluding agents such as Ivalon particles or absolute alcohol are now preferred. Hepatic metastases as well as primary hepatic tumors have been embolized with success (Fig. 13). The liver provides an ideal environment for tumor embolization because of its dual blood supply with the tumor fed primarily by the hepatic arteries as opposed to normal liver tissue receiving the majority of its nutrients from the portal system. Therefore, embolization of the hepatic arteries proximal to the hepatic sinusoids should primarily affect the tumor and much less the normal hepatic parenchyma. 3 Tumors in the head and neck region and the extremities have been embolized for palliation and before surgery to reduce blood loss during surgery.3 Parathyroid adenomas have been successfully embolized simply by overinjection with highly concentrated contrast material. Parathyroid adenomas may be uniquely suitable for this kind of treatment because of their single artery blood supply and small size. 3 Tumor embolization has to deal with the so-called post embolization syndrome particularly well known from renal tumor embolization. In our experience, most of the pain immediately following embolization is the

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Figure 13. Palliative embolization of recurrent hepatoma following left hepatic lobectomy. A, CT scan showing low-density tumor in the central portion of the liver. B, Common hepatic arteriogram showing hypervascular tumor typical of hepatoma with extension into the hepatic vein (arrow). Primary blood supply originating from an enlarged left central hepatic artery. C, Patency of portal vein and intrahepatic branches during the venous phase of the celiac arteriogram. Portal vein patency is considered a prerequisite for safe arterial embolization. D, Total hepatic artery occlusion following embolization with Ivalon particles.

result of ischemia of normal parenchyma. Necrosis of the tumor may cause pain, fever, nausea, and rises in blood urea nitrogen (BUN), lactic dehydrogenase (LDH), and white blood count. Before a renal tumor is embolized, a urine culture is obtained to identify a potential source for ascending infection and abscess formation. 3 During hepatic embolization, infarction of the gallbladder is a major risk. 3 Retrograde spill of embolic material may complicate any embolization. Embolic occlusion of inferior mesenteric branches with resulting infarction of the colon and embolic spill into lower extremities with distal vascular occlusion has been reported. 3 The indication for tumor embolization should be reached jointly by clinician and interventional radiologist. The patient has to be made aware of the chances for success and the risks of the procedure. Sometimes it is better to perform embolotherapy in stages rather than trying to occlude everything in one session.

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Figure 13 (Continued). E, Post-embolization common hepatic arteriogram showing immediate collateralization to the tumor via right hepatic artery branches. F, Following right hepatic artery embolization, all tumor supply is occluded. G, eT scan after embolization showing central tumor necrosis. The patient remains with stable disease one year after embolization.

PERCUTANEOUS TRANSLUMINAL ANGIOPLASTY (PTA)

Introduction of the limited-expansion balloon catheter by Gruntzig and co-workers in 197423 expanded application of this technique originally conceived by Charles Dotter in the early 1960'S.11 The Dotter system consisted of a sequence of coaxial catheters to open and expand a stenotic or occluded vascular segment, which in turn resulted in a rather large arterial puncture site. The limited-expansion balloon catheter, referred to as balloon catheter, reduces the size of the arterial entry and limits the effect to the arterial segment treated (Fig. 14). The great majority of arterial occlusive disease is due to atherosclerosis. Experimental studies of normal and diseased arteries in vivo and on cadaver material have investigated the mechanism by which balloon expansion acts on the vascular wall. The atherosclerotic plaque becomes fissured and is pushed into the vessel wall. There is also some longitudinal displacement of plaque. Plaque is essentially incompressible. 7 In order to achieve long-term patency of the vessel, plastic deformity of the elastic components of the vessel wall needs to be achieved. Expansion of the dis-

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Figure 14. Present version of limited expansion balloon dilatation catheter. This catheter is inflated in the left common iliac artery. Note the metallic markers on the catheter shaft indicating the extension of the expandable segment.

eased artery needs to exceed the lumen to be reestablished by about 20 per cent, allowing for some degree of elastic recoil. 56 Dilatation of largercaliber arteries such as the iliac and superficial femoral arteries allows not only observation of the angiographic changes following balloon dilation but also direct arterial pressure measurement. PTA should abolish or reduce a pressure gradient to a nonsignificant level « 10 mm Hg at rest). If the initial dilatation does not produce adequate lumen size or reduction of pressure, a ~arger balloon is required. In renal and coronary angioplasty, the arteriographic guidance is in most cases the only reliable parameter to judge the therapeutic effect. Again, inadequate dilation with residual stenosis as seen on post-PTA arteriography should prompt introduction of a larger-caliber dilation balloon. The better the blood How through the dilated lumen, the less the risk of subsequent thrombus formation and the better the likelihood of longterm patency. 51 Platelet aggregation inhibitors such as aspirin are routinely administered before and after PTA. When larger caliber arteries are dilated, post-angioplasty heparinization is not required. In smaller arteries, particularly the renal and coronary arteries, arterial spasm needs to be treated immediately to avoid thrombus formation. Nitroglycerin or calcium-blocking agents are injected directly into the arteries. PTA of larger-caliber arteries such as the iliac arteries carry the best presently established 3 to 5 year patency rates of 79 per cent or better (Fig. 15). In the femoropopliteal segment, 5-year patency is in the neighborhood of 65 to 70 per cent. 48 Since the procedure requires only an arterial catheter, repeat dilatation is indicated should stenosis or occlusion recur. When results of PTA are compared to those of surgical bypass grafting, one needs to bear in mind that the procedures are not competitive

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Figure 15. Transluminal dilatation of iliac artery stenosis. A, Typical ring stenosis of the left iliac artery with an 80-mm Hg pressure gradient. This stenosis may occlude at any time without change in the patient's symptomatology. B, Post-PTA without residual pressure gradient. Slight irregularity at the site of previous stenosis. With adequate blood How through the dilatation site, the initial luminal irregularity will regress.

but complementary. Regional stenosis or occlusion is quite well treated with PTA, whereas long segments of occlusion exceeding 8 to 10 cm in the femoropopliteal region or short occlusion of iliac arteries are indications for bypass or iliac endarterectomy. Since athersclerotic disease is progressive over years, PTA should be carried out as soon as the patient becomes symptomatic with lower extremity claudication, in order to prevent an initial femoral artery stenosis from becoming an occlusion for which PTA has a lower chance of success (Fig. 16). Similarly, patients with Leriche syndrome should be investigated early and subjected to PTA before segmental iliac occlusion occurs. These early treated cases should have cure rates similar to that achieved with surgical bypass grafting. Some specific considerations warrant renal artery angioplasty. This treatment modality is indicated for (1) treatment of renin-dependent hypertension, and (2) increase of renal blood flow to improve renal function. Technical success of PTA of the renal artery is expected in 85 to 90 per cent of all procedures attempted (Figs. 17 and 18).50 Short-term and some of the long-term failures are related to inadequate balloon expansion, athersclerotic plaques extending into the abdominal aorta, and direct trauma to the renal artery by guidewire or catheter, resulting in thrombosis (Fig. 19). Renal artery thrombosis and the need for surgical intervention to salvage the kidney occurs in about 1 per cent. Heparin is administered rou-

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Figure 16. Percutaneous transluminal angioplasty (PTA) of distal right superficial femoral artery. A, Typical tight-ring stenosis of the distal superficial femoral artery at the predilection site, the adductor canal entry. This stenosis has a high potential of total occlusion and retrograde thrombosis. B, After PTA, there is slight residual luminal irregularity but no pressure gradient. Good results are expected owing to excellent blood How through reestablished arterial lumen. Patient regained right foot pulses and healed transmetatarsal ampuitation.

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Figure 17. Percutaneous transluminal angioplasty (PTA) of fibromuscular renal artery stenosis and renin-dependent hypertension. A, Flush aortogram shOwing discrete stenosis of the distal right renal artery with post-stenotic dilatation. Decreased right nephrogram. 4:1 right-to-left renal vein renin ratio. B, Immediately post-PTA from left axillary approach with widely patent renal artery. Some intrarenal artery spasm. Patient's blood pressure returned to normal.

tinely during PTA of the renal artery in' bolus doses of 2500 to 5000 units. After the procedure, systemic heparin should be instituted for 12 to 24 hours, during which time the risk of platlet aggregation and thrombus formation is highest. Considering the simplified work-up for renal hypertension using digital venous arteriography and the less than 0.1 per cent mortality from

Figure 18. Percutaneous transluminal angioplasty (PTA) of stenotic left renal artery bypass graft. A, Flush aortogram showing tight stenosis at renal artery graft anastomosis. Patient's renal function had deteriorated. Note stenosis of right renal artery with shrunken right kidney. B, Post-PTA of left graft anastomosis with increased renal blood flow. Patient's renal function improved.

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Figure 19. Atherosclerotic stenosis of origin of the left renal artery unsuitable for percutaneous transluminal angioplasty. Plaque extension into the abdominal aorta (arrows) renders balloon dilatation ineffective.

PTA, risks and costs of the diagnosis and treatment of renal hypertension have significantly decreased and should liberalize indications for such work-up. Considering that renal hypertension is the only potentially curable form, an appropriate work-up should be performed before the hypertensive patient is committed to life-long drug treatment. 20 REGIONAL THROMBOLYSIS

Low-dose infusion of streptokinase or urokinase directly into the occluding arterial thrombus has gained increasing acceptance, and numerous patients with acute graft thrombosis, acute thrombosis during angioplasty, and acute spontaneous vascular thrombosis superimposed on arterial stenosis have been successfully treated with a regimen consisting of streptokinase infused at a rate of about 5000 units per hour or urokinase at a rate of 40,000 units per hour for 12 to 36 hours (Fig. 20). This regimen requires placement of a small-caliber catheter in direct proximity to the occluding thrombus with adjustment of catheter position while thrombolysis is in progress. In theory, low-dose arterial infusion avoids the systemic effects of venous infusion. However, since systemic effects cannot be excluded, a satisfactory clotting profile is required before lysis therapy. Thrombus time and fibrinogen levels are determined periodically during infusion of the lytic agent. If fibrinogen falls rapidly, reduction in dose or interruption of the lytic agent is indicated. 27 Sometimes unexplained failure of thrombolysis during streptokinase infusion may be related not only to inactivating antibodies but also to the relatively dilute infusion of streptokinase preparations. If this represents a problem, urokinase is the better choice. Thrombi more than 10 days old are less readily lysed. However, there are several reports in which chronic arterial occlusions were successfully opened with streptokinase infusions. 37 The same controversy exists for emboli of unknown age. In any event, the best results should be obtained with acute thrombotic occlusions with the thrombolytic agent delivered directly into the occluding thrombus.

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Figure 20. Thrombolysis of acute thrombotic occlusion of bypass graft. A, Abdominal aortogram showing occluded right limb of aortobifemoral bypass graft. B, After 5000 units of streptokinase per hour for 6 hours through crossover catheter into right iliac graft; subtotal thrombolysis. C, After additional 16 hours of streptokinase infusion, reopening of the entire iliac graft; some residual thrombosis at the femoral graft anastomosis. D, Mter 36 hours of total streptokinase infusion; the entire graft reopened. Stenosis at popliteal graft anastomosis is probable cause for acute thrombosis. Revision of this anastomosis required to allow longterm patency of graft. Patient on full heparinization.

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PERCUTANEOUS BILIARY DRAINAGE

Obstructive jaundice may be relieved by (1) surgical bilioenteric anastomosis, (2) retrograde endoscopic placement of a stent, or (3) percutaneous transhepatic placement of a drainage catheter or stent endoprosthesis. Each of the three methods has its advantages and disadvantages. Surgery for malignant biliary obstruction is accompanied by a significant perioperative mortality,15 Preoperative percutaneous or retrograde drainage may improve postoperative survival. When resection for cure is not feasible, malignant biliary obstruction is best palliated with a much lower immediate risk by either retrograde or percutaneous transhepatic drainage. This is particularly the case in locally advanced carcinoma of pancreas, metastatic obstruction of the porta hepatis, cholangiocarcinoma, and intrahepatic tumor obstruction. Compared to the percutaneous approach, the retrograde endoscopic approach has the advantage of lower risk of infection and no externally protruding catheter through the skin; however, it is poorly suited for porta hepatis and intrahepatic obstructions, and the caliber of drainage catheters is limited. Percutaneous biliary drainage (PBD) offers several advantages: accommodation of large drainage catheters (size 12 to 14 French) for more effective longterm drainage applicable to porta hepatis and intrahepatic obstruction with one or more catheters, relative ease of catheter management by the patient or family member, and exchangeability of catheters with minimal discomfort once a tract is established. Detailed descriptions of percutaneous biliary drainage technique can be found in publications by several groups. 24, 32, 38 The procedure is performed under appropriate antibiotic coverage. Correction of a reversible bleeding diathesis precedes any transhepatic instrumentation. A dilated intrahepatic duct is fairly easy to puncture from a lateral approach with a 21gauge needle (Fig. 21). Small amounts of dilute contrast are injected just sufficient to allow the passage of a larger caliber sheath needle, a guidewire, and placement of a 5- or 6-French catheter (Fig. 22). Then drainage of

Figure 21. Percutaneous transhepatic cholangiogram drainage showing total occlusion of distal common bile duct in a 58-yearold woman with carcinoma of the head of the pancreas,

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Figure 22. From left to right: 21 gauge Chiba puncture needle and stylet for initial transhepatic cholangiogram; l8-gauge sheath needle for selective puncture of dilated intrahepatic biliary duct; O.038-inch exchange guidewire for advancement of final drainage catheter; O.02l-inch flexible-tipped guidewire, which will traverse a 2l-gauge Chiba needle for insertion of intermediate-sized dilating catheter prior to final catheter placement.

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Figure 23, Externally draining biliary catheter placed in a 50-year-old man with common bile duct obstruction secondary to carcinoma of the head of the pancreas.

inspissated bile is instituted preferably over the next 24 hours with a catheter secured in the ductal system and connected to an external drainage system (Fig. 23). This stage alone can be offered to operable candidates for preoperative decompression. In a day or two, the obstruction can usually be traversed by a flexible guidewire which is passed into the distal duodenum. Then the transhepatic tract is dilated and an 8-Fr. pigtail catheter placed with its tip in the duodenum. Internal antegrade drainage can proceed once the intrahepatic ducts are decompressed (Fig. 24). Within a week, a 10- or 12-Fr. catheter can be accommodated for long-term drain-

Figure 24. Antegrade drainage by a catheter advanced into the third portion of the duodenum in a 60-year-old woman with pancreatic carcinoma. This patient has been followed as an outpatient for 6 months on internal drainage.

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age. Later;12-:'or 14-Fr.silicone catheters are exchanged as needed. After one week the cutaneous entry site of the catheter no longer requires dressing and is best kept open and dry. Elastic tape attaches the outside portion of the catheter to the skin (Fig. 25). The risk of no intervention must be considered with likelihood of intractable pruritus, cholangitis, sepsis, and liver failure. An acute complication rate for PBD of up to 14 per cent has been reported in different series. 5• 8, 24, 32, 38, 44 These complications include sepsis, peritonitis, and hemorrhage primarily with hemobilia or traumatic arteriovenous fistula, subcapsular hematoma, pancreatitis, pneumothorax, and catheter dislodgement. Adherence to proper technique, such as entering bile ducts as pe-. ripherally as possible, and using coaxial needles can largely avoid traumatic complications. The risks then are related primarily to bacteremia. Therefore, all procedures are performed under adequate blood levels of antibiotics effective against enteric organisms. Also, bile needs to be drained immediately and effectively. Definitive diagnostic cholangiography may be deferred until after decompression by external biliary drainage. Long-term complications of percutaneous biliary drainage are primarily ascending cholangitis and hepatic abscess, sometimes related to progressive biliary obstruction by an underlying malignant process. A permanent stent endoprosthesis can be introduced percutaneously in patients who cannot manage an externally protruding device, especially when only short-term survival is expected. 6, 17,30 Since the long-term pat-

Figure 25. A, A 55-year-old woman had cholangiocarcinoma involving junction of right and left hepatk duct systems (Klatzkin's tumor), giving nearly complete obstruction. B, Each system was separately drained; the left internally into the common bile duct, where the normal ampullary sphincter will regulate emptying into the duodenum, preventing reflux. The right duct obstruction could not be trasversed and an externally draining catheter was anchored well into a side branch. This tumor is characteristically slow to progress and presents a difficult and frequently impossible task for resection. With adequate biliary drainage it is possible to maximize their survival potential.

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IIlWOC HOSPITAL DlSTRIC'J

Figure 26. Placement of a 12-French endoprosthesis for antegrade biliary drainage in a 55year-old woman with pancreatic carcinoma. A cholecystojejunostomy performed several months earlier recently stopped functioning. The patient was unable to manage an externally protruding catheter. This stent apparently continued to function well until the patient's death 3 months later.

ency rate has not yet been determined, this approach is not recommended when long-term survival is anticipated (Fig. 26). PERCUTANEOUS ABSCESS DRAINAGE The radiologic approach to drainage of hepatic, abdominal, or pelvic abcesses is similar to that for biliary obstruction. Following initial identification and localization of the collection by ultrasound or CT, needle entry is usually sonographically directed, and aftef aspiration of a specimen for culture, a guidewire is advanced through the needle followed by progressively larger catheters for external drainage and decompression. If required, 12-Fr. catheters or even larger ones can be introduced. Defervescence usually occurs within 24 hours; although, the catheter will be left in place at least 12 to 20 days. The cavity may be opacified at any time by injection of contrast which outlines its extent and any tract extensions (Fig. 27). As in biliary instrumentation, appropriate antibiotic coverage is established before puncture of any abscess. Coverage can be changed as directed by the culture. The catheter may be Hushed on a daily basis if needed to assist in drainage. Successful drainage implies no recurrence and has been achieved in 70 to 85 per cent of cases. Failures may result from multiloculated abscess cavities, perhaps with hematoma, or in instances of internal fistulization. Potential complications include sepsis, pneumothorax, and vascular trauma. More detailed reviews of this subject are available in the recent literature.9, 21, 22, 53

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Figure 27. A, Real-time sector scan of subhepatic abscess collection showing cursor for guidance of puncture needle. Patient was a 55-year-old woman who developed an abscess following cholecystectomy. B, Real-time sector scan shows needle (arrow) within the collection. C, Contrast medium outlines abscess cavity; note tip of right hepatic lobe as a negative shadow (arrow). D, Final placement of multi-end-hole pigtail drainage catheter within abscess cavity.

REFERENCES 1. Alavi, A., and Ling, E. J.: Localization of gastrointestinal bleeding: Superiority of -Tc sulfur colloid compared with angiography. A.J.R, 137:741-748, 1981. 2. Athanasoulis, C. A., Pfister, RC., Greene, R E., et al.: Interventional Radiology. Philadelphia, W. B. Saunders Co., 1982. 3. Barth, K. H.: Clinical applications of embolotherapy. In Kadir, S., Kaufman, S. L., Barth, K. H., et al. (eds.): Selected Techniques in Interventional Radiology. Philadelphia, W. B. Saunders Co., 1982. 4. Barth, K. H., White, R I., Jr., Kaufman, S. L., et al.: Embolotherapy of pulmonary arteriovenous malformations with detachable balloons. Radiology, 142:599--606, 1982. 5. Berquist, T. H., May, G. R, Johnson, C. M., et al.: Percutaneous biliary decompression: Internal and external drainage in 50 patients. A.J.R., 136:901-906, 1981. 6. Burcharth, F.: A new endoprosthesis for nonoperative intubation of the biliary tract in malignant obstructive jaundice. Surge Gynecol. Obstet., 146:76-78, 1978. . 7. Casteneda-Zuniga, W., Edwards, J. E., Zollikofer, C., et al.: The mechanism of balloon angioplasty. Radiology, 135:565--571, 1980. 8. Clark, RA., Mitchell, S. E., Colley, D. P., et al.: Percutaneous catheter biliary decompression. A.J.R, 137:503-509, 1981. 9. Clark, R A., and Towbin, R: Abscess drainage with CT and ultrasound guidance. Radiol. Clin. North Am., 21:445-459, 1983.

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10. Coleman, c., Yukiyoshi, K., Castaneda-Zuniga, W., et al.: Dilatation of nephrostomy tracts for percutaneous renal stone removal. Semin. Intervent. Radio!., 1:50--55, 1984. 11. Dotter, C. T., and Judkins, M. P.: Transluminal treatment of arteriosclerotic obstruction. Description of a new technique and a preliminary report of its application. Circulation, 30:654-670, 1964. 12. Doppman, J. L., and Pevsner, P.: Embolization of arteriovenous malformations by direct percutaneous puncture. A.J.R., 140:773-778, 1983. 13. Eisenberg, H., and Steer, M. L.: The nonoperative treatment of invasive pyloroduodenal hemorrhage by retracted autologous clot embolization. Surgery, 79:414-420, 1976. 14. Engelstat, B. L., and Hattner, R. S.: New scintigraphic methods of detecting and localizing gastrointestinal bleeding. Applied Radiol/NM, July/Aug., 1983, pp. 85-94. 15. Feduska, N. J., Dent, T. L., and Lindenauer, S. M.: Results of palliative operations for carcinoma of the pancreas. Arch. Surg., 103:330-334, 1971. 16. Fellows, K. E., Khaw, K. T., Schuster, S., et al.: Bronchial artery embolization in cystic fibrosis: Technique and long-term results. J. Pediatr., 095:959-963, 1979. 17. Ferrucci, J. T., Jr., and Mueller, P. R.: Interventional radiology of the biliary tract. Gastroenterology, 82:974-985, 1982. 18. Ferrucci, J., Jr., Wittenberg, J., Sarno, R., et al.: Fine needle transhepatic cholangiography: A new approach to obstructive jaundice. A.J.R., 127:403-407, 1976. 19. Ferrucci, J., Jr., and Wittenberg, J.: Refinements in Chiba needle transhepatic cholangiography. A.J.R., 129:11-16, 1977. 20. Foster, J. F., Dean, R. H., Pinkerton, J. A., et al.: Ten years experience with the surgical management of renovascular hypertension. Ann. Surg., 177:755-766, 1973. 21. Gerzof, G. G., Spira, R., and Robbins, A. H.: Percutaneous abscess drainage. Semin. Roentgeno!., 16:62-71, 1981. 22. Gronvale, S., Gammelgaard, J., Haubek, A., et al.: Drainage of abdominal abscesses guided by tomography. A.J.R., 138:527-529, 1982. 23. Gruntzig, A., and Hopff, J.: Perkutane Rekanalisation chronishcher arterieller Verschlusse mit einem neuen Dilatationskatheter. Modifikation der Dotter-Technik Dtsch. Med. Wochenschr., 99:2502-2511, 1974. 24. Hoevels, J., Lunderquist, A., and Thse, J.: Percutaneous transhepatic intubation of bile ducts for combined internal/external drainage in preoperative and palliative treatment of obstructive jaundice. Gastrointest. Radio!., 3:23-31, 1978. 25. Hoevels, J., and Nilsson, V.: Intrahepatic vascular lesions following nonsurgical percutaneous transhepatic bile duct intubation. Gastrointest. Radio!., 5:127-135, 1980. 26. Kadir, S., Kaufman, S. L., Barth, K. H., et al.: Selected Techniques in Interventional Radiology. Philadelphia, W. B. Saunders Co., 1982. 27. Katzen, B. T., and VanBreda, A.: Low dose streptokinase in the treatment of arterial occlusions. A.J.R., 136:1171-1178, 1981. 28. Lemarque, J. L., and Senac, J. P.: Therapeutic ahgiography in hemoptysis-Results of 100 cases. In Anacker, H., Gulotta, V., Rupp, N. (eds.): Percutaneous Biopsy and Therapeutic Vascular Occlusion. Stuttgart, Georg Thieme, 1980. 29. Margulis, A.: Interventional diagnostic radiology: A new subspecialty. A.J.R., 99:761, 1967. 30. Mendez, G., Russell, E., Leve, J. V., et al.: Percutaneous brush biopsy and internal drainage of biliary tree through endoprosthesis. A.J.R., 134:653-659, 1980. 31. Mueller, P. R., van Sonnenberg, E., Ferrucci, J. T., Jr.: Percutaneous biliary drainage: Technical and catheter-related problems in 200 patients. A.J.R., 138:17-23, 1982. 32. Nakayama, T., Ikeda, A., and Okuda, K.: Percutaneous transhepatic drainage of the biliary tract. Gastroenterology, 74:554-559, 1978. 33. Nusbaum, M., Baum, S., Blakemore, W. S., et al.: Clinical experience with selective intra-arterial infusion of vasopressin in the control of gastrointestinal bleeding from arterial sources. Am. J. Surg., 123:162-172, 1972. 34. Okuda, K., Tanikawa, K., Emura, T., et al.: Nonsurgical percutaneous transhepatic cholangiography-Diagnostic significance in medical problems of the liver. Dig. Dis., 19:21-36, 1974. 35. Owman, T., Lunderquist, A., Alumark, A., et al.: Embolization of the spleen for treatment of splenomegaly and hypersplenism in patients with portal hypertension. Invest. Radiol., 14:457-464, 1979. 36. Palmaz, J. C., Newton, T. H., Reuter, S. R., et al.: Particulate intra-arterial embolization in pelVic arteriovenous malformations. A.J.R., 137: 117-122, 1981.

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37. Poliwoda, H., Alexander, K., Buhl, V., et al.: Treatment of chronic arterial occlusions with streptokinase. N. Engl. J. Med., 280:689-692, 1969. 38. Pollock, T. W., Ring, E. J., Olenga, J. A., et al.: Percutaneous decompression of benign and malignant biliary obstruction. Arch. Surg., 114:148-151, 1979. 39. Porstmann, W.: Ein neuer KorseU-Ballon-Katheter zur transluminalen Rekanalisation nach Dotter unter besonderer Berucksichtigung von Obliterationen an den Beckenarterien. Radiol. Diagn. (Berl.), 14:239-244, 1973. 40. Porstmann, W., and Wierny, L.: Intravasale Rekanalisation inoperabler arterieller Obliterationen. Zentralbl. Chir. 92[Suppl.]:1586, 1967. 41. Prochaska, J. M., Flye, M. W., and Johnsrude, I. S.: Left gastric artery embolization . control of gastric bleeding: A complication. Radiology, 107:521-522, 1973. 42. Remy, J., Arnaud, A., Fardou, H., et al.: Treatment of hemoptysis of embolization of bronchial arteries. Radiology, 122:33-37, 1977. 43. Remy, J., Smith, M., Lemaitre, L., et al. Treatment of massive hemptysis by occlusion ofa Rasmussen aneurysm. A.J.R, 135:605-606,1980. 44. Ring, E. J.: Interventional radiology of the biliary tract. Bull N. Y. Acad. Med., 56:575580,1980. 45. Ring, E. J., and McLean, G. K.: Interventional Radiology: Principles and Techniques. Boston, Little, Brown and Co., 1981. 46. Rosch, J., DoUer, C., and Brown, M. J.: Selective arterial embolization. Radiology, 102:303-306, 1972. 47. Smith, R K., and Arterburn, G.: Detection and localization of gastrointestinal bleeding using Tc-99m pyrophosphate in vivo labeled red blood cells. Clin. Nucl. Med., 5:5560,1980. 48. Spence, R K., Freiman, D. B., Gatenby, R, et al.: LOng-term results of transluminal angioplasty of the iliac and femoral arteries. Arch. Surg., 116:1377-1386, 1981. 49. Spigos, D. G., Tan, W. S., Mozes, M. F., et al.: Splenic embolization. Cardiovasc. Intervent. Radiol., 3:282-288, 1980. 50. Sos, T. A., Pickering, T. G., Sniderman, K., et al.: Percutaneous transluminal renal angioplasty in renovascular hypertenSion due to atheroma or fibromuscular dysplasia. N. Engl. J. Med., 309:274-279, 1983. 51. Sos, T. A., and Sniderman, K. W.: Percutaneous transluminal angioplasty. Semin. Roentgenol., 16:26-41, 1981. 52. Uflacker, R, Kaemmerer, A., Neves, C., et al.: Management of massive hemoptysis by bronchial artery embolization. Radiology, 146:627-634, 1!)83. 53. vanSonnenberg, E., Ferrucci, J. T., Jr., Mueller, P. R, et al.: Percutaneous drainage of abscesses and fluid collections: Technique, results, and applications. Radiology, 142:110, 1982. 54. Waltman, A. C., Greenfield, A. J., Novelline, R A., et al.: Pyloroduodenal bleeding an.d intra-arterial vasopressin: Clinical results. A.J.R, 133:643, 1979. 55. Wholey, R K. H., Chamorro, H. A., Ras, G., et al.: Bronchial artery embolization for massive hemoptysis. J.A.M.A., 236:2501-2504, 1976. 56. Wolf, G. L., LeVeen, R F., and Farrar, P.: Elastic recoil of normal rabbit arteries following angioplasty in vivo. Presented to the 32nd Annual Meeting of the Association of University Radiologists, Newport Beach, California, 1984. Georgetown University Hospital 3800 Reservoir Road, N. W. Washington, D.C. 20007