Fetal bladder histology in posterior urethral valves and the prune belly syndrome.

Bladder histology was reviewed in fetuses with posterior urethral valves and the prune belly syndrome, and compared with that of controls. Fetuses with posterior urethral valves had increased muscle thickness (1.7 +/- 0.3 versus 0.9 +/- 0.2 mm.) and a slightly increased ratio of connective tissue (38 +/- 6 versus 31 +/- 7%). Those with the prune belly syndrome fell into 2 groups: 1 had anatomical evidence of obstruction, increased muscle thickness and a normal ratio of connective tissue (2.2 +/- 0.6 mm. and 28 +/- 9%), while 1 had no evidence of obstruction and thin bladders with increased connective tissue (0.8 +/- 0.4 mm. and 45 +/- 12%). These results suggest that the phenotypic appearance of the prune belly syndrome may result from either a mesenchymal defect or urinary tract obstruction.