The origin of vesico-ureteric reflux in male newborns: further evidence in favour of a transient fetal urethral obstruction.

Objective: To present further arguments supporting a transient urethral obstruction occurring during early fetal development as an explanation of the origin of vesico-ureteric reflux (VUR) in baby boys.

Methods: The findings of ultrasonography and voiding cysto-urethrography (VCUG) in 25 baby boys with VUR were reviewed, studying mainly bladder and urethral anomalies on VCUG and bladder-wall thickness on ultrasonography.

Results: A bladder or urethral anomaly was found in 15 patients, comprising isolated posterior urethral dilatation in five, posterior urethral dilatation with a bladder anomaly in four, tubular appearance of the urethra in two and bladder neck hypercontractility with diverticulae in four. Bladder-wall thickness ranged from 1 to 8 mm (mean 3.7) and in eight patients, the thickness exceeded 5 mm.

Conclusions: The bladder and urethral anomalies found in this series of patients with neonatal VUR could be explained by a transient bladder outlet obstruction that possibly occurred in utero. These findings support the theory that a significant number of cases of VUR seen in baby boys result from a transient fetal urethral obstruction.