Digital Subtraction Angiography for Postoperative Evaluation of Renal Arterial Reconstruction

0022-534 7/82/1271-0014$02.00/0

Vol. 127, January Printed in U.S.A.

THE JOURNAL OF UROLOGY

Copyright © 1982 by The Williams & Wilkins Co.

DIGITAL SUBTRACTION ANGIOGRAPHY FOR POSTOPERATIVE EVALUATION OF RENAL ARTERIAL RECONSTRUCTION ANDREW C. NOVICK, EDWARD BUONOCORE

AND

THOMAS F. MEANEY

From the Departments of Urology and Radiology, Cleveland Clinic Foundation, Cleveland, Ohio

ABSTRACT

Digital subtraction angiography after peripheral intravenous injection of contrast material is a new method to evaluate the cardiovascular system. Digital subtraction angiography was obtained postoperatively in 21 patients undergoing renal revascularization for treatment of hypertension and/ or preservation of renal function. Digital subtraction angiography provided excellent visualization of the reconstructed renal arterial supply in all cases. The advantages and limitations of this technique in the evaluation of patients with renovascular disorders are discussed. 1.0 mg. glucagon was given intravenously just before injection of the contrast medium. The equipment for obtaining images with digital subtraction angiography consisted of a specially designed computer system integrated with a fluoroscopic and radiographic apparatus for digitalization, manipulation and display of images. The specific details of this unit are described elsewhere. 2 There were no complications of digital subtraction angiography in any of these patients. The extrahilar renal arterial supply to the repaired kidney, either from the aorta (figs. 1 and 2), splenic and hepatic (fig. 3) or iliac vessels (fig. 4) was well visualized and found to be unobstructed in all cases. In most studies the intrarenal arterial anatomy was not delineated completely. In some patients an IVP was obtained immediately after and from the same dose of contrast medium administered for the digital subtraction angiography (fig. 5).

Renovascular reconstruction is an established mode of treatment for patients with hypertension and/or azotemia resulting from renal artery disease. In our hospital aortorenal bypass is the method of revascularization used in most cases, except in patients with severe aortic atherosclerosis or intrarenal branch arterial lesions, in which cases alternate surgical approaches are preferable. 1 Postoperative evaluation of the efficacy of vascular reconstruction is accomplished by monitoring the blood pressure and the level of renal function, and by obtaining functional or anatomic radiographic studies, such as isotope renography, excretory urography (IVP) or repeat angiography. Standard catheter angiography provides the only method for directly visualizing the newly fashioned renal arterial supply, yet this is an invasive study that often is unnecessary when the patient's clinical course combined with isotope renography indicates a successful outcome ofrevascularization. Digital subtraction angiography after peripheral intravenous injection of modest amounts of contrast material is a new method to evaluate the human cardiovascular system with important advantages over conventional angiography. 2- 4 We evaluated the efficacy of digital subtraction angiography in delineating renal arterial anatomy after surgical revascularization.

DISCUSSION

The use of photographic subtraction techniques for studying areas of radiographic interest was described by des Plantes in 1935 and is used commonly. 5 Arteriography by the intravenous injection of contrast material was described in 1939. 6 However, its usefulness has been limited by the need for large doses of contrast medium and the relative insensitivity of radiographic film to small attenuation differences between tissues and contrast material. Digital subtraction angiography has developed from advances in digital image processing that, combined with radiographic techniques used in computerized tomography, have yielded contrast resolution ability not possible previously.2-4 Digital subtraction angiography allows accurate, relatively noninvasive visualization of the cardiovascular system with an unusually high contrast sensitivity after conventional amounts of intravenously administered contrast material (fig. 6). The basic principles enabling satisfactory digital subtraction angiography are similar to those that have been described for intravenous arteriography. 7 These include the rapid delivery of a bolus of contrast medium through a large caliber introductory needle, taking care to avoid interstitial extravasation of the contrast material. The presence of adequate cardiac output for rapid dissemination of contrast medium throughout the cardiovascular system is an important prerequisite for high quality digital subtraction angiography imaging. Patients are hydrated well before the study to ensure optimal renal perfusion and to limit the occurrence of contrast-induced nephrotoxicity. Patients are ini;;tructed to avoid the V alsalva maneuver during performance of digital subtraction angiography to prevent slowing of cardiac filling and trapping of contrast material in the arm or neck veins. In some patients intestinal peristaltic activity limits proper visualization of the abdominal aorta and renal

CLINICAL MATERIAL AND RESULTS

Our study includes 21 patients undergoing renal revascularization from April 1980 to January 1981, in whom postoperative digital subtraction angiography was obtained. All of these patients had significant renal artery stenosis diagnosed preoperatively on conventional angiography. In all cases arterial reconstruction was done for the treatment of renovascular hypertension and/or the preservation of renal function. The operations included aortorenal bypass with a simple or branched saphenous vein graft in 14 patients and autotransplantation in 6. One patient with significant aortic atherosclerosis underwent simultaneous right hepatorenal and left splenorenal bypass. Postoperatively, arterial hypertension was cured or improved, the level of renal function was unchanged or improved, and technetium renal scanning showed satisfactory perfusion and function of the revascularized kidney in all cases. Each of the 21 patients underwent digital subtraction angiography from 5 days to 5 weeks postoperatively, either while in the hospital or as outpatients. To perform digital subtraction angiography a 16 gauge needle was inserted into a peripheral vein of the forearm and attached to a pressure injector. The usual dose of contrast medium did not exceed 0.5 to 1.0 ml./kg. of body weight and the average single injection ranged from 30 to 50 ml. of 76 per cent Renografin at 10 to 12 cc per second, followed by 25 cc of 5 per cent dextrose flush. In each patient Accepted for publication March 27, 1981. 14

DIGI'TAL SIIBTE.A.. CTlf)l¼' A~TGI0GRAF1-i~~-

15

. FIG. 1. A, preoperative conventional aortogram in (i9-year-old man with hypertension demonstrates total occlusion of left renal artery _and high grade stenos1s of nght renal artery. B, digital subtraction angiogram after left aortorenal saphenous vem bypass illustrates patent graft (nght arrow) to revascularized kidney. Area of stenosis involving proximal right renal artery (left arrow) also is demonstrated.

FIG. 2. A, preoperative conventional aortogram shows high grade proximal stenosis of 2 left renal arteries (arrows). B, left aortorenal with branched saphenous vein graft was performed. Postoperative digital subtraction angiogram shows patent branched graft to-end to 2 renal arteries (arrows).

FIG. 3. A, preoperative conventional aortogram in 60-year-old woman with bilateral high grade renal artery stenosis (arrows) and significant aortic atherosclerosis. B, digital subtraction angiogram after right hepatorenal and left splenorenal bypass operation shows patent vascular anastomoses to both kidneys (arrows).

16

NOVICK, BUONOCORE AND MEANEY

arteries. This problem usually can be avoided by intravenous administration of glucagon just before the injection of the contrast material.

Fm. 4. Digital subtraction angiogram after autotransplantation shows patent end-to-end anastomosis of renal artery to hypogastric artery (arrow).

Although the technology and performance of digital subtraction angiography are in their relative infancy this new modality has important application to patients with renovascular disorders. Buonocore and associates recently did an initial comparative study of conventional aortography and digital subtraction angiography in evaluating the renal arteries of 30 patients. 8 All 30 patients were studied on ii;;l occasions with both modalities and a total of 70 renal arteries was evaluated. On conventional angiography 21 renal arteries were normal and 49 had varying degrees of atherosclerosis or fibrous dysplasia. In an evaluation of the diagnostic grading of renal artery lesions with each technique the over-all accuracy of digital subtraction angiography compared to standard aortography was 71 per cent (50 of 70). In those patients in whom digital subtraction angiography did not correlate with standard aortography the main reasons were suboptimal concentration of contrast medium in the renal artery because of severe proximal stenosis, poor visualization of the renal artery caused by overlying mesenteric vessels and failure to visualize adequately the oblique origin of the renal artery on an anteroposterior view because of the overlapping lateral aortic wall. Some of these problems can be overcome by changes in positioning, injection technique and instrumentation, while others represent inherent deficiencies that are common to conventional flush aortography as well. In the present study digital subtraction angiography provided

Fm. 5. A, preoperative conventional aortogram (subtraction technique) in 56-year-old woman with hypertension shows severe aortic atherosclerosis and high grade proximal left renal artery stenosis. Since iliac vessels were relatively free of disease autotransplantation of left kidney was performed. B, postoperative digital subtraction angiogram demonstrates patent end-to-side anastomosis ofrenal artery to left common iliac artery. C, IVP from same dose of contrast medium demonstrates excellent function of left renal autograft.

FIG. 6. A, digital subtraction angiogram in 56-year-o!d man with hypertension demonstrates mild aortic atherosclerosis, normal left renal artery and high grade proximal right renal artery stenosis from atherosclerosis. B, digital subtraction angiogram in 22-year-old woman with hypertension demonstrates cmooth aorta, normal left renal artery and stenosis of mid right artery from fibrous dysplasia.

excellent visualization of renal arterial supply after surgical revascularization in all cases. It also was possible, when clinically indicated, to obtain an IVP from the same dose of contrast medium used for digital subtraction angiography. There are several reasons for the improved efficacy of digital subtraction angiography in this setting compared to the initial screening of patients for renal artery stenosis. First, the renal artery anastomoses generally were done either to the infrarenal aorta or to the iliac arteries, where there was less interference from overlying nonrenal arteries. In the performance of aortorenal revascularization, particularly on the left side, the bypass graft generally is brought directly off the lateral aortic wall, facilitating visualization of the origin of the graft. In addition, the excellent flow through the reconstructed arteries yielded good concentration of contrast medium and, thereby, provided satisfactory visualization of the vascular repair. Although there were no such cases in this series failure to visualize the repaired renal artery or the demonstration of an area of stenosis on digital subtraction angiography would strongly suggest a technical problem (arterial thrombosis or stenosis) after revascularization. Since digital subtraction angiography to date has not provided uniformly reliable visualization of intrarenal arteries it is not as useful in the evaluation of patients who have undergone extracorporeal revascularization for extensive branch renal artery disease. In such cases selective catheter angiography remains the most reliable method of u,c;uHcosw,,:. postoperative intra.renal ~,,m-vsHy The potential usefulness of subtraction angH)gi·a1Jh) in patients with renovascular disease encompasses more than screening and early evaluation. This also can be used as a serial for progress of patients with known renal being followed or for extended of after either revascularization or percutaneous translu-· minal angioplasty. A further benefit of digital subtraction angiography is the availability of quantitative data, which enables determination of the accumulation and rate of transit of contrast material in different areas of the cortex and medulla. 2 Such information may have clinical application to the diagnosis of other renal disorders and this concept is currently under evaluation. In conclusion, digital subtraction angiography is a promising addition to the diagnostic armamentarium for renovascular disorders and has proved reliable in the postoperative evaluaHH,~.OvO.H f

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tion of patients undergoing renal arterial reconstruction. Digital subtraction angiography is a rapid, relatively noninvasive technique that can be performed safely on an outpatient basis. This method offers several advantages over standard catheter angiography and represents an important advance in the imaging of the cardiovascular system. REFERENCES l. Novick, A. C. and Stewart, B. H.: Surgical treatment ofrenovascular

hypertension. Curr. Prob. 16; 1, 1979. 2. Meaney, T. F., Weinstein, M. Buonocore, E., Pavlicek, W., Borkowski, G. P., Gallagher, J. H., Sufka, B. and MacIntyre, W. J.: Digital subtraction angiography of the human cardiovascular system. Amer. J. Roentgen., 135: 1153, 1980. 3. Crummy, A. B., Strother, C. M., Sackett, J. F., Ergun, D. L., Shaw, C. G., Kruger, R. A., Mistretta, C. A., Turnipseed, W. D., Lieberman, R. P., Myerowitz, P. D. and Ruzicka, F. F.: Computerized fluoroscopy: digital subtraction for intravenous angiocardiography and arteriography. Amer. J. Roentgen., 135: 1131, 1980. 4. Reuter, S. R.: Digital subtraction angiography. Amer. J. Roentgen., 135: 1316, 1980. 5. des Plantes, B. G. Z.: Subtraktion: eine rontgenograhische Methode zur separaten Abbildung bestimmter Teile des Objekts. Fortsch. Geb. Roentgenstr., 52: 69, 1935. 6. Robb, G. P. and Steinberg, I.: Visuaiization of the chambers of the heart, the pulmonary circulation and the great blood vessels in heart disease; preliminary observations. Amer. J. Roentgen., 42: 14, 1939. 7. Steinberg, L and Stein, H. L.: Intravenous angiocardiography, abdominal aortography and peripheral arteriography with single pressure Arner. Roentgen., 92: 893, 1964. 8. Buonocore, ,VI-" of the abdominal aorta and renal arteries: comparison raphy. Unpublished data. EDITORIAL COMMENT Digital subtraction angiography undoubtedly will gain rapid acceptance as a routine imaging technique. Digital subtraction angiography does not provide the detail and clarity of a selective angiograrn but the technique will be useful because procedures can be performed on an outpatient basis, the examination is less invasive and less expensive than catheter angiography, and the images are sufficiently detailed for many clinical situations. The major manufacturers of x-ray equipment are all currently involved in the development of digital subtraction systems. S.S.S.