454: Are current protocols to assess candidacy for vesicoamniotic shunt placement for fetal lower urinary tract obstruction (LUTO) adequate?

Abstract

To assess which parameters used for invasive fetal renal testing were associated with neonatal survival in fetuses diagnosed with LUTO. A retrospective chart review was conducted of all patients referred with LUTO. LUTO was defined as fetal megacystis with low amniotic fluid volume (maximum vertical pocket < 3 cm). Fetal renal testing was defined as the assessment of urinary electrolytes by serial vesicocenteses, or serum β2-microglobulin levels via single or serial cordocentesis. Patients were deemed candidates for vesicoamniotic shunting (VAS) if the results of these tests were within previously published norms. 43 fetuses met the above criteria. 29 of these 43 elected to undergo invasive fetal renal assessment, of which outcomes were available for 28 patients. After fetal renal testing, 11 met criteria for VAS, and 9 chose to undergo shunting; 33.3% (3/9) had 30-day survival in the VAS group compared to 0% (0/2) in the non-VAS group. Of the 17 patients who were not candidates for VAS, 5 elected to undergo VAS despite counseling; 60% (3/5) of these patients reached 30-day survival compared to 25% (3/12) in the non-VAS group. Comparing patients that met criteria and elected to undergo VAS to those that did not meet criteria but desired shunt placement regardless, 30-day survival rates were 33.3% versus 60.0% (p=0.58). The only prenatal assessment tool associated with improved neonatal survival was a decrease in fetal serum β2-microglobulin level over time (P=0.040). Although the sample size in this study is small, the findings suggest that the current paradigm for fetal renal testing may be suboptimal. Further studies are required to determine the efficacy of serial fetal serum β2-microglobulin as a predictor of survival in these patients.