Fetal Urine Cystatin C as a Predictor of Postnatal Renal Function in Bilateral Uropathies

Abstract

Fetal obstructive uropathies are among the most frequent anomalies diagnosed by prenatal ultrasound. Prenatal management of obstructive uropathies depends on the evaluation of renal function. Although the prognosis is good in unilateral cases, bilateral uropathies are associated with a wide spectrum of outcomes ranging from perinatal death from pulmonary hypoplasia and terminal renal failure to survival with normal renal function. In the mildest cases and in the most severe forms of fetal uropathy, sonography alone is a good predictor of outcome, and invasive approaches based on fetal blood or fetal urine biochemistry are therefore unnecessary. In contrast, in bilateral uropathies with normal amniotic fluid volume or moderate oligohydramnios and without major structural anomaly of the renal parenchyma, neonatal survival is expected, but postnatal morbidity is difficult to predict by sonography alone (1)(2)(3). In the fetus, serum creatinine cannot be used as a marker of glomerular filtration rate (GFR) because it crosses the placenta and is cleared by the mother (4). Fetal serum β2-microglobulin has been evaluated in a few cases, but more experience is necessary (5)(6)(7). Fetal urinalysis is probably the most accurate approach to quantitative evaluation of renal function. This is because during fetal life, the mother supplies the fetus through the placenta with balanced nutrients, and fetal homeostasis is ensured without the intervention of the fetal kidneys. Therefore, the composition of fetal urine depends …