Scintigraphy and Doppler ultrasonography for the evaluation of obstructiveurinary calculi

Forty-seven patients with unilateral obstructive calculi (12 males and 35 f emales) were submitted to Tc-99m-diethylene triamine pentaacetic acid (DTPA ) or Tc-99m-dimercaptosuccinic acid (DMSA) scans for assessment of renal fu nction. The scans revealed unilateral functional deficit in 68 and 66% of t he patients, respectively. A calculus size of 1.1 to 2.0 cm was significant ly associated with deficit detected by DTPA, but duration of obstruction an d calculus localization were not. After relief of the obstruction, the mean percent renal function of the affected kidney was found to be significantl y increased from 25 +/- 12% to 29 +/- 12% in DTPA and from 21 +/- 15% to 24 +/- 12% in DMSA. Initial Doppler ultrasonography performed in 35 patients detected an increased resistive index in 10 (29%). In the remaining patient s with a normal resistive index, ureteral urinary jet was observed, indicat ing partial obstruction. The high frequency of renal function impairment de tected by DTPA and of tubulointerstitial damage detected by DMSA as well as the slight amelioration of unilateral renal function after relief of obstr uction suggest that scintigraphy assessment may help evaluate the unilatera l percentage of renal function and monitor renal function recovery when it occurs. The presence of a urinary jet detected by Doppler ultrasonography f urther indicates the severity of obstruction and the recovery prognosis.