0D22-5347/8l/:_253 .. o379$C2.0C':/O TH~ JeuRUAL 07 UROLOGY Copyright© 1981 by The 'vVtlliams & ;Nilkins Co. Vol. 125, }\II21·ch Printed in U.S.A. USE THE RADIONUCLIDE WASHOUT TEST IN EVALUATION OF SUSPECTED UPPER URINARY TRACT OBSTRUCTION KEY H. ST AGE AND SAM LEWIS From the Divisions of Urology and Nuclear Medicine, University of Texas Southwestern Medical School, Dallas, Texas ABSTRACT The use of the computerized quantitative renal scan associated with the standard renogram obtained during furosemide-induced diuresis provides useful information in the assessment of suspected upper tract obstruction. With the use of 99 mtechnetium diethylenetriaminepentaacetic acid or 131 iodine hippuran quantitative renal scans were obtained and renograms were generated before and after intravenous furosemide injection. Rapidity of diuretic-induced radionuclide wash- out, as well as determination of glomerular filtration rate or effective renal plasma flow on the affected side, provides objective information with regard to renal parenchymal loss as well as upper tract emptying. We herein report our experience with 19 such patients. The radionuclide washout test is obtained easily, informative and may replace more invasive diagnostic measures. The clinician long has been presented with the problem of accurate evaluation of upper urinary tract dilatation. Many methods have been used to assess the significance of this entity, including excretory urography (IVP), radionuclide renography, fluoroscopy, retrograde pyelography and urodynamic studies incorporating direct percutaneous nephrostomy. Our experi- ence with 19 patients is reported using computer-assisted radi- oisotope renography and furosemide-induced diuresis to assess the significance of upper tract dilatation. MATERIALS AND METHODS All patients underwent a radionuclide renal scan using either 131 iodine ( 131 I) hippuran or 99 mtechnetium diethylenetriamine- pentaacetic acid ( 99 mTc DTP A) with dosage adjusted for body weight and age. 1 • 2 All studies were done with the patients in a well hydrated state, and intravenous fluids were administered before the injection of radionuclide in an attempt to provide maximum spontaneous diuresis. Scans obtained using 131 I hip- puran were recorded on an ADAC computer using a high energy parallel hole collimator with the window centered at 360 kev. The base line quantitative renal scan was obtained using a well established computer program, recording continuous 20-second frames for the first 15 minutes.2 The scans obtained using 99 mTc DTP A were recorded on continuous 30-second frames on a Medical Data Systems computer using a low energy diverging collimator centered at a 140 kev. window setting. Fifteen min- utes after injection of either radionuclide 0.5 mg./kg. furosemide was injected intravenously and the recorded frames were done for an additional 15 minutes. After furosemide-induced diuresis renal histograms were generated for the entire 30-minute inter- val to assess the effect of the diuretic on the base line curves. Individual percentage of contribution to total renal function for each kidney was calculated using light pen defined areas of interest with background subtraction. The defined areas of interest included the entire kidney and renal pelvis but excluded the ureters. Background conected renal histograms were gen- erated for each kidney and examined to assess the effect of diuretic-induced renal washout. Renal parenchymal assessment was obtained by determination of individual effective renal plasma flow to each kidney when 131 1 hippuran was used in the aforementioned computer program. RESULTS were in the pediatric population with young adults comprising the next most populous group. After the studies were reviewed the patients were divided most easily into 4 categories described previously by O'Reilly and associates. 3 Response 1. The normal response was observed in 2 patients (11 per cent). In this group the initial and diuretic exaggerated response revealed a normal renogram with increased radionu- clide washout after the injection of furosemide (fig. 1). Prompt uptake of radionuclide was observed in the first l to 5 minutes of the study with spontaneous washout of radionuclide even before furosemide was given. This pattern excluded virtually any evidence of obstruction, representing non-pathologic ana- tomically large collecting systems noted on IVP. Response 2. This pattern was observed in 9 patients (47 per cent). Of these individuals 6 had a clinical diagnosis of ureter- opelvic junction obstruction, l had an ileal conduit with sus- pected ureteroileal stenosis, l had upper tract dilatation after pyeloileocystostomy and l had distal ureterovesical junction obstruction. The renograrns of these patients demonstrated obstructive patterns on the base line curve and after injection of diuretic. The furosemide had no effect on the shape of the curve and effectively demonstrated significant obstruction (fig. 2). The majority were candidates for operative correction and significant ureteropelvic junction obstruction was demonstrated at the time of operation in 3 patients. The remaining individuals are being followed as operative candidates. Response 3a. In these 4 patients (21 per cent) the initial reno5ram curve showed the obstructive pattern. However, after injection of furosemide the renogram demonstrated prompt effective washout of the radionuclide (fig. 3). Of the 4 patien:"ts l was noted to have bilateral mild hydronephrosis 4 months post partum, l had minimal upper tract dilatation in a solitary kidney, 1 was evaluated for residual bilateral hydronephrosis after previous bilateral ureteropelvic junction repair and 1 was studied for possible ureteropelvic junction obstruction and flank pain. These patients demonstrated atonic dilatation of the upper tract with poor emptying in the base line state but completely adequate upper tract drainage after diuresis. All 4 patients currently are followed conservatively. Response 3b. These 4 patients (21 per cent) demonstrated an initial obstructive pattern on the base line renogram and showed moderate to minimal washout of radionuclide with diuresis after injection of furosemide. Of these 4 patients 1 underwent retrograde pyelography on the basis of the radio- We studied 19 patients ranging in age from 10 months to 60 nuclide study and an unsuspected ureteropelvic junction ob- years, with an average of 22.9 years. The majority of patients struction was demonstrated, requiring operative repair (fig. 4). Accepted for publication June 13, 1980. Two other patients had suspected ureteropelvic junction ob- 379