Diuretic Doppler sonography following successful repair of renal obstruction in children.

The measurement of resistive index (RI = [peak systolic velocity--end diastolic velocity]/peak systolic velocity) by Doppler sonography has demonstrated variable reliability as an indicator of pediatric urinary obstruction. By modifying Doppler studies with the addition of furosemide (diuretic Doppler sonography), we previously found significant differences between 10 nonobstructed and 10 obstructed kidneys in children (median age 7 months). The obstructed kidneys have since undergone surgical repair, and postoperative reevaluation has been performed by diuretic Doppler sonography and diuretic renography. Diuretic Doppler sonography was performed on well hydrated catheterized patients, with resistive index measurement of the renal interlobar and arcuate arteries obtained before and 10 minutes after 1 mg./kg. furosemide infusion. Following surgical repair of obstruction all 10 kidneys had stable glomerular filtration rate with improved pelvic emptying times as demonstrated by half-time. Of 6 kidneys evaluated by diuretic Doppler sonography before 3 months 2 had resistive index levels greater than 75. Of the 9 kidneys measured at 3 months or more postoperatively all had resistive index values of less than 75, even after furosemide infusion (5 kidneys underwent repeat evaluation). In our study the previously demonstrated post-diuretic elevation of resistive index in pediatric urinary obstruction was eventually reversed following surgical repair. Diuretic Doppler sonography appears to be a promising noninvasive method for evaluating pediatric hydronephrosis, providing an alternative physiological parameter with which to measure renal obstruction.