Congenital syndrome. 'prune belly' syndrome is a congenital disorder of the urinary system, characterized by a triad of symptoms: (no abdomen wall muscles, bladder dysfunction, undesc. Testes) the syndrome is named for the mass of wrinkled skin that is often present on the abdomen. Prune belly syndrome is a rare, genetic, birth defect affecting about 1 in 40, 000 births. about 97% of those affected are male.