PROGNOSTIC SIGNIFICANCE OF CAPTOPRIL RENOGRAPHY FOR MANAGING CONGENITAL UNILATERAL HYDRONEPHROSIS MINU BAJPAI,* A. PURI, M. TRIPATHI AND A. MAINI From the Departments of Paediatric Surgery and Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India ABSTRACT Purpose: In this prospective study we evaluated the results of captopril enhanced diuretic renography in patients with congenital unilateral ureteropelvic junction type hydronephrosis. Captopril renography helps to distinguish patients who have renin-angiotensin system activa- tion from those in whom it is not yet activated. Renin-angiotensin system activation heralds the beginning of compensatory vasoactive response in the kidney. Identifying grades of such activa- tion may help in determine the end points of nonoperative management. Materials and Methods: We prospectively studied 25 patients with suspected unilateral uret- eropelvic junction obstruction treated at our department. A prenatal diagnosis was made in 60% of cases. Patient age was 1 to 144 months (mean 40) and the male-to-female ratio was 4:1. Followup was 6 to 72 months (mean 30). Patient evaluation and analysis included sonography, standard diuretic and captopril renography, glomerular filtration rate, serum creatinine and blood pressure. The indications for surgery were symptoms, differential function below 35%, or a documented decrease of 10% or more during followup. Activation of the renin-angiotensin system was considered positive when split renal function decreased significantly by 5% or more in an obstructed system on a post-captopril study. The results of captopril renography were examined retrospectively in patients who required surgery according to preexisting criteria. Results: Society for Fetal Urology hydronephrosis grade was II to IV in 8, 10 and 7 renal units, respectively. The renin-angiotensin system was activated in 8 of the 25 cases (32%) of unilateral ureteropelvic junction obstruction. In 15 patients there was no change on pre-captopril and post-captopril studies and in 2 split renal function on the obstructed side marginally increased on the post-captopril study. Surgical correction was required in only 6 of the 8 patients with renin-angiotensin system activation. Of those who required surgery hydronephrosis was grades II to IV in 3, 1 and in 2 patients, respectively. Conclusions: In the current study renin-angiotensin system activation correlated with the need for surgery in 75% of the cases of congenital unilateral ureteropelvic type hydronephrosis. Since captopril serves to identify patients who have renin-angiotensin system activation, it may also be possible to grade this activation. Our preliminary results show that there may be a role for captopril renography for identifying the risk group for surgical intervention. KEY WORDS: kidney, hydronephrosis, ultrasonography, captopril, renin-angiotensin system With the advent of prenatal ultrasound the management of congenital hydronephrosis has been revolutionized. In the past most patients presented with symptoms such as urosep- sis, pain, hematuria, palpable mass or failure to thrive, and so the need for treatment was apparent. However, with the detection of incidentally diagnosed asymptomatic cases man- agement continues to evolve. Many surgeons perform conservative treatment for sus- pected congenital unilateral ureteropelvic junction ob- struction unless differential function decreases below 35%. 1, 2 To delay surgery until measurable deterioration in renal function has occurred seems to deny the patient the benefit of state-of-the-art management. Therefore, it is important to identify the time when decompensation starts, before the kidney becomes permanently damaged in these cases. During the initial stages of obstruction the kidney function is maintained within normal limits by vasoactive compensatory mechanism, namely the renin- angiotensin system. 3–5 Sustained obstruction may cause these mechanisms to fail and expose the kidneys to per- manent functional deterioration. Renin-angiotensin sys- tem activation can be detected by captopril renography, which has been shown to be a minimally invasive and highly sensitive diagnostic tool for identifying renin- angiotensin system activation in patients with renovascu- lar hypertension. 6, 7 We prospectively studied the role of diuretic captopril renography in the management of sus- pected congenital unilateral ureteropelvic junction ob- struction. MATERIAL AND METHODS This prospective study was performed at the department of pediatric surgery at our institution. The study sample consisted of 25 consecutive patients with suspected unilateral ureteropel- vic junction obstruction treated at our department and regis- tered for followup at the pediatric urology clinic. The medical records of these patients were reviewed to note age at presen- tation, current age, duration of followup, surgical treatment, trends of renal function tests and changes in the upper tract on ultrasonography. Hydronephrosis in each renal unit was graded on ultrasound according to the Society for Fetal Urology (SFU) grading system as 1—mild, 2—moderate and 3 or 4 —se- vere. We used 99m technetium-diethylenetriaminepentaacetic acid ( 99m Tc-DTPA) for diuretic renography. Imaging was re- Accepted for publication June 14, 2002. * Requests for reprints: Department of Paediatric Surgery, All India Institute of Medical Sciences, New Delhi-110029, India. 0022-5347/02/1685-2158/0 Vol. 168, 2158 –2161, November 2002 THE JOURNAL OF UROLOGY ® Printed in U.S.A. Copyright © 2002 by AMERICAN UROLOGICAL ASSOCIATION,INC. ® DOI: 10.1097/01.ju.0000034367.40739.6f 2158