Spontaneous resolution of an in utero perirenal urinoma associated with posterior urethral valves

Ultrasound imaging of a 26-week-gestation fetus demonstrated a large, nonemptying bladder. At 27 weeks, a distended, thick-walled bladder, left hydronephrosis, and a perirenal urinoma were present, without ascites. Observation was undertaken, as the amniotic fluid volume was normal. At 29 weeks, the left perirenal fluid collection persisted but, at 30 weeks, was absent. After delivery at 36 weeks, no ultrasound evidence for perirenal urinoma or ascites was present. Isotope renal scan showed preserved renal function bilaterally. This case illustrates that in utero urinomas associated with posterior urethral valves can resolve spontaneously, with preservation of renal function.