Prenatally diagnosed unilateral hydronephrosis: prognostic significance of plasma renin activity

Controversy surrounds the optimal management of prenatally diagnosed hydronephrosis due to technical limitations in accurately quantifying the degree of obstruction at the ureteropelvic junction. These patients are regularly investigated for ureteropelvic junction obstruction, severe abdominal pain, abdominal lump and deterioration in renal function. In this descriptive study we quantify plasma renin activity as an additional measure to evaluate renal outcome.

In 90 consecutive children with prenatally diagnosed unilateral hydronephrosis an association was sought between changes in plasma renin activity, split renal function, glomerular filtration rate and serum creatinine. Patients with split renal function less than 35% at presentation were excluded from the study. Mean followup was 50.1 +/- 15.9 months (range 24 to 87). Pyeloplasty was performed if patients became symptomatic or split renal function decreased more than 10% during followup.

Increase in plasma renin activity and decrease in split renal function and glomerular filtration rate were noted in patients being followed nonoperatively (40 patients) and in those requiring pyeloplasty (50). However, these parameters were more pronounced in the operated group. In the latter group plasma renin activity increased by 64.7% between initial (15.9 ng) and preoperative (26.2 ng) values, and became normal postoperatively. In nonoperatively followed patients plasma renin activity continued to increase until the last followup.

Plasma renin activity progressively increased from the time of presentation to the time of surgery. It was reduced and stabilized in all children postoperatively. Plasma renin activity reflects obstructive stress, and precedes parameters of actual renal injury, such as split renal function and glomerular filtration rate.