Diuretic renography in the evaluation of neonatal hydronephrosis: is it reliable?

Arguments against the use of diuretic renography in the assessment of newborn hydronephrosis include immature function of neonatal kidneys, previously reported poor diuretic response and nonreproducible drainage patterns. To address these concerns we reviewed the initial and followup renal scans of 17 neonates with hydronephrosis without ureterectasis diagnosed by perinatal ultrasonography. All patients were evaluated with an initial diuretic renal scan up to the age of 28 days, and all had normal cystograms. A total of 19 dilated kidneys was studied of which 13 ultimately required pyeloplasty and 6 were managed nonsurgically. Patient study parameters included age and weight at the time of each renal scan, side of hydronephrosis, differential function of each kidney, pre-diuretic and post-diuretic urine output, and drainage half-time of each kidney. The diuretic renal scans followed a standardized protocol. There was no statistically significant difference between neonatal and followup differential function (p > 0.05), and the correlation coefficient was highly significant (r = 0.968). Comparison of response to diuretic stimulation (ml./kg. per minute) revealed no statistically significant difference as the patients aged with brisk urine output 3 to 5 times greater than previously reported. The distribution and mean drainage half-times for normal nonhydronephrotic kidneys were similar when comparing those performed as neonates and at followup. Hydronephrotic kidneys managed nonsurgically maintained almost identical patterns. Those repaired surgically demonstrated appropriate improvement in drainage but function remained unchanged. These results refute each of the criticisms against the use of diuretic renography to evaluate neonatal hydronephrosis and demonstrate its reliability in neonates.