Biochemical diagnosis in prenatal uropathy

Thirty-two fetuses, six with prune-belly syndrome, seven with renal cyst, 19 with obstructive uropathy, underwent intrauterine fluid aspiration during weeks 15-37 of gestation. Fluid samples were analysed for Na, K, creatinine, urea, alpha 1-, and beta 2-microglobulin. Aspirate concentrations of sodium below 130 mmol/L and creatinine above 115 mumol/L indicate an active kidney and exclude a renal cyst. However, aspirates from fetal cysts or fetuses with obstructive uropathy showed analyte concentrations for sodium, potassium, creatinine, and urea corresponding to extracellular fluid (ECF). In conclusion fluid aspirates of fetuses with ultrasonographically detectable cystic cavities in the abdomen should be examined for sodium and creatinine to assess remaining renal function for planning of obstetric management.