The pathogenesis of prune belly.

Three neonates were born with marked abdominal muscular laxity from three different conditions (posterior urethral valves, nonimmune ascites, and intestinal duplication); two had fetal abdominal distention by ascites documented in utero by obstetric ultrasonographic examination. Another fetus, whose abdominal distention was relieved at 21 weeks' gestation by in utero decompression of urinary obstruction, was born with only mild abdominal changes, which suggests that the "prune belly" phenotype can resolve if distention is relieved early enough. These observations suggest that the abdominal laxity in prune belly syndrome is a simple deformation secondary to abdominal stretching and distention during fetal development and is not an intrinsic generalized mesodermal abnormality.