Diuretic radionuclide renography in upper urinary tract obstruction.

Diuretic renography using radioidine sodium hippurate and a frusemide stimulus was used to differentiate between obstructive and nonobstructive dilatation of the urinary tract. Information was recorded by a gamma camera on line to a computer. Sixty-seven uretero-renal units (URU) were studied in 33 patients with an average age of 91/2 years. The diuretic renogram correctly indicated obstructions in 18 URU but gave false positive results in another five. Of these five, four had severely impaired function. The renogram indicated nonobstruction in 49 URU, and gave false negative results in another two; of these two one patient had a duplex kidney with a poorly functioning ureteric segment and the other patient had gross reflux and megaureters. The diuretic renogram is useful in the investigation of equivocal upper urinary tract obstruction but may be unreliable in situations of inadequate renal function.