Development of a fetal renal function test using endogenous creatinine clearance.

Selecting appropriate management for the fetus with obstructive uropathy depends on our ability to accurately assess the severity of existing renal damage and to predict the potential for recovery of renal function if the obstruction is relieved. Diagnosis and treatment would be markedly enhanced by a simple, safe, quantitative fetal renal function test. To answer the question of whether endogenous fetal creatinine clearance (CrC) is an accurate measure of glomerular filtration rate (GFR) in the obstructed fetal kidney, we compared fetal CrC to a standard test for GFR--iothalamate clearance (IC). Six fetal lambs underwent unilateral ureteral ligation at 60 to 63 days gestation (term = 145 days). The contralateral unobstructed kidneys served as a control. At a second operation at 113 to 120 days, renal function was measured by hourly split urine collections for determination of CrC, IC, and fractional sodium excretion on each side over a 4-hr study period. There was excellent correlation of CrC with IC in all kidneys (r = 0.997, P less than 0.001, y = 1.14 x). Compared to the control side, the obstructed fetal kidneys had significantly decreased GFR and abnormal tubular function with marked sodium loss.(ABSTRACT TRUNCATED AT 250 WORDS)