The wrinkled 'prune-like' appearance of the abdomen is due to deficiency of the abdominal wall muscles. Prune belly syndrome, which occurs almost exclusively in boys, is often accompanied by undescended testes and urinary tract abnormalities such as megacystis, grossly dilated ureters and hydronephrosis. Bowel malrotation and musculoskeletal and cardiac abnormalities may also be present.