The role of diuretic renography in the evaluation of obstructed hydronephrosis after pediatric pyeloplasty

Background: The purpose of this study was to clarify the value of renal drainage half-time in the evaluation of pediatric hydronephrosis after dismembered pyeloplasty. Methods: We reviewed the records of 30 children who underwent dismembered pyeloplasty for unilateral ureteropelvic junction obstruction with no other associated urological abnormality. The follow-up duration was more than 5 years for all patients. Pre- and postoperative evaluation included technetium-99m dimercaptosuccinic acid (^99mTc- DMSA) renal scan, technetium-99m diethylenetriaminepentaacetic acid ( ^99mTc-DTPA) diuretic renography, and ultrasonographic examination. According to postoperative renal drainage half-time on diuretic renography, patients were divided into 2 groups: group A with normal renal drainage and group B with prolonged renal drainage for evaluation of their renal functional status. Results: Postoperative diuretic renography revealed normal drainage (group A) in 54% of patients and prolonged drainage (group B) in 46%. The anteroposterior diameter (APD) of the renal pelvis of all patients showed improvement after pyeloplasty. There was no significant difference in improvement of the renal pelvic APD between the 2 groups. Furthermore, 92% of group A and 91% of group B maintained stable or had improved differential renal function (DRF) postoperatively. Conclusions: Drainage half-time is not a reliable parameter for diagnosing obstructed hydronephrosis after pediatric pyeloplasty. We suggest that the renal pelvic APD and DRF should be considered when postoperative obstructed hydronephrosis is diagnosed using the criterion of prolonged renal drainage half-time on diuretic renography.