Natural History of Fetal Lower Urinary Tract Obstruction with Normal Amniotic Fluid Volume at Initial Diagnosis.

OBJECTIVE: The aim of this study was to define the natural history of lower urinary tract obstruction (LUTO) with normal midgestational amniotic fluid volumes.

MATERIALS AND METHODS: We performed a retrospective review of 32 consecutive patients with LUTO with normal midgestational amniotic fluid volume followed at 11 North American Fetal Therapy Network (NAFTNet) centers from August 2007 to May 2012. Normal amniotic fluid volume was defined as an amniotic fluid index (AFI) of ≥9 cm.

RESULTS: The mean gestational age (GA) and AFI at enrollment were 23.1 ± 2.1 weeks and 15.8 ± 3.9 cm, respectively. The mean GA at delivery was 37.3 ± 2.8 weeks. The mean creatinine level at discharge was 1.2 ± 0.8 mg/dL. Perinatal survival was 97%. Twenty-five patients returned for serial postnatal assessment. Renal replacement therapy (RRT) was required in 32%. Development of oligohydramnios and/or anhydramnios, development of cortical renal cysts, posterior urethral valves, prematurity, and prolonged neonatal intensive care unit stay were associated with need for RRT (p < 0.05) by univariate analysis. By multivariate analysis, preterm delivery remained predictive of need for RRT (p = 0.004).

CONCLUSION: Prenatal diagnosis of LUTO with normal midgestational amniotic fluid volumes is associated with acceptable renal function in the majority of patients. Approximately one-third of these children require RRT. Surrogate markers of disease severity appear to be predictive of need for RRT.