prune-belly syndrome, a syndrome, occurring almost exclusively in males, in which the lower part of the rectus abdominis muscle and the lower and medial parts of the oblique muscles are absent, the bladder and ureters are usually greatly dilated, the kidneys are small and dysplastic with hydronephrosis, and the testes are undescended. The abdomen is protruding and thin-walled with wrinkled skin, giving the syndrome its name.