RT Book, Section A1 Bianchi, Diana W. A1 Crombleholme, Timothy M. A1 D'Alton, Mary E. A1 Malone, Fergal D. SR Print(0) ID 1106399576 T1 Hydronephrosis: Bladder Outlet Obstruction T2 Fetology: Diagnosis and Management of the Fetal Patient, 2e YR 2015 FD 2015 PB McGraw-Hill Education PP New York, NY SN 978-0-07-144201-5 LK obgyn.mhmedical.com/content.aspx?aid=1106399576 RD 2024/10/10 AB Key PointsPosterior urethral valves (PUVs) are the most common cause of bladder outlet obstruction in males.PUVs account for 10% of all urologic anomalies detected by prenatal ultrasound.PUVs have a broad range of severity from completely asymptomatic to complete obstruction, oligohydramnios, pulmonary hypoplasia, and renal dysplasia.Oligohydramnios due to a PUV, if untreated, is associated with nearly uniform neonatal mortality due to pulmonary hypoplasia.Sonographic prognostic criteria predicting poor outcome include presence of subcortical cysts and increased echogenicity of the kidneys, which are associated with renal dysplasia.Fetal urine electrolytes (Na <100, Cl <90, Osm <210, β2-microglobulin <6) are associated with preserved renal function and favorable prognosis with treatment.Fetal urine electrolytes are only valid for fetuses at 20 weeks of gestation or later.Treatment options include vesicoamniotic shunt placement, fetoscopic ablation of PUV, and open fetal surgery for vesicostomy.Fifty percent of successfully treated fetuses with PUV develop growth failure and chronic renal failure requiring dialysis and/or transplantation.