Management and outcome of antenatally diagnosed hydronephrosis.

From March 1989 to December 1992, we encountered 25 kidneys in 21 patients with a suspicious ureteropelvic junction (UPJ) obstruction detected only on prenatal ultrasound. In all these patients other urological abnormalities were excluded by voiding cystourethrography and other radiological findings. Diuretic renography (DR) was initially performed at an age ranging from 15 days to 32 months in all patients and repeated a total of 39 times. Both the split renal function (SRF) and diuretic drainage half-time clearance (DT1/2) of radioagent were within their normal ranges in the case of 15 (60%) of the kidneys on initial DR. In these kidneys, there were no aggravated signs on repeated DR. Decreased SRF was found in 3 kidneys (12%) on initial DR. Of these, the renal function spontaneously reverted to normal in 2 cases with bilateral hydronephrosis. Another 1 kidney revealed significant UPJ obstruction assessed by pressure flow study and continuous nephrostomy drainage had brought relief from the obstruction 1 year later. Prolonged DT1/2 with normal SRF was found in 7 (28%) kidneys. The renal function did not deteriorate and the diuretic response improved on repeat DR except for 1 kidney, whose function deteriorated and on which ultimately, pyeloplasty was performed at 7 months of age. Prenatally diagnosed hydronephrosis is usually asymptomatic and clinically significant UPJ obstruction should be always verified. Although even today there is still no examination which can detect a definite obstruction, we can identify one as significant by careful repeat examinations and thus avoid unnecessary surgery without causing any renal deterioration.