[Congenital hydronephrosis detected by prenatal ultrasonography: the effect of pyeloplasty on renal function]

Prenatal detection of congenital hydronephrosis has raised new questions with regard to the need of management and the indications for operation. Moreover, there is considerable controversy whether or not pyeloplasty improves long-term renal function. We evaluated the operative results of this entity under the setting of well defined indications for surgery.

The indications for pyeloplasty included Society for Fetal Urology-grade (SFU-grade) 3 and grade 4 hydronephrosis on ultrasonogram together with obstructive pattern on modified "Well Tempered" diuretic renogram. We analysed the postoperative changes of ultrasonographic findings, differential renal function, and renogram patterns in 28 children with unilateral hydronephrosis detected prenatally.

Of the patients, 27 had grade-4 hydronephrosis on preoperative ultrasonogram. Pyeloplasty was effective in decreasing the grade of dilatation in all kidneys except one. Of the involved renal units, 14 (50%) had reduced differential renal function less than 45% on the preoperative renogram. Differential renal function increased significantly by absolute value of 5% or greater in 8 kidneys (29%), but decreases in 5 kidneys (18%). In the remaining 15 kidneys (54%) there was no significant differences between pre- and post-operative differential renal function. Postoperative diuretic renogram changed to non-obstructive pattern in 26 kidneys (93%). Another 2 kidneys showed hypofunctioning pattern.

The results suggest that, although pyeloplasty decreases ultrasonographic dilatation of hydronephrosis and improves excretory pattern of diuretic renogram, significant increase of differential renal function is expected in only one third of the involved kidneys.