Patterns of Congenital Lower Urinary Tract Obstructive Uropathy: Relation to Abnormal Prostate and Bladder Development and the Prune Belly Syndrome

The pathogenesis of lower urinary tract obstruction is disputed, particularly its relation to both abnormal prostatic development and the prune belly syndrome (PBS). In an attempt to clarify this issue we examined 11 males (17–38 weeks gestation) with PBS who were autopsied at our institution. The lower urinary tract was embedded intact and prepared as serial histologic sections. Of the 11 cases, 8 demonstrated mechanical obstruction of the lower urinary tract. In five of these eight cases, a “flap-valve” structure was formed by an abnormal angulation between the prostatic and penile portions of the urethra. These had dilated, thin-walled bladders and prostates and moderate to severe renal dysplasia. One of the eight cases had a valve-like obstruction at the level of the mid-prostatic urethra associated with a complex cloacal malformation and a thin-walled bladder, another case had an epithelial plug at the penile meatus, and the last of the eight cases had a posterior urethral valve. The three remaining cases showed no mechanical obstruction. However, each had megacystis with marked thickening, interstitial fibrosis, and disarray of smooth muscle bundles in the bladder wall. In 10 cases, the prostate had no or only sparse, flattened glands. These results suggest that the abnormal development of the prostate in PBS may be explained as a pressure-induced dysplasia rather than a primary maldevelopment. The findings further suggest that abnormal prostatic development and the prune belly syndrome may arise from either anatomic obstruction of various types or functional obstruction from megacystis.