Neonatal extracorporeal membrane oxygenation in congenital urinary tract obstruction with pulmonary hypoplasia: a case complicated by alveolar capillary dysplasia emphasizing importance of early rapid genetic testing.

A late preterm male infant born at 36 weeks and 2 days of gestation with birth weight of 2.5 kg and prenatally diagnosed bilateral hydronephrosis, megaureter, urinomas, and failed fetal shunt placement in the setting of anhydramnios developed severe hypoxemic respiratory failure shortly after birth. Despite surfactant, inhaled nitric oxide, and vasoactive support, refractory hypoxemia with severe pulmonary hypertension (oxygenation index of 56) necessitated venoarterial extracorporeal membrane oxygenation (ECMO) at 9 h of life. His course was complicated by hemodynamic instability, transfusion requirements, anticoagulation titration, and fluid overload necessitating continuous renal replacement therapy. Serial echocardiograms showed worsening right ventricular dysfunction, and he failed multiple clamp trials. Rapid Exome Sequencing, drawn on day of ECMO initiation confirmed de novo pathogenic variant in FOXF1, diagnostic of congenital alveolar capillary dysplasia with misaligned pulmonary veins (ACDMPV). Given the universally fatal prognosis, care was redirected after multidisciplinary discussions. This case highlights the importance of early genomic testing in certain ECMO candidates to guide timely clinical decision-making and resource stewardship while also underscoring the need for deeper investigation into CAKUT-ACD (CACD) overlap phenotypes, an area that remains poorly characterized and that may influence prognosis and management strategies.