This malformation complex occurs in males and includes a triad of abnormalities:
1) deficiency of abdominal musculature
2) urinary tract abnormalities
The clinically apparent deficiency of abdominal wall musculature results in a characteristic flaccid, wrinkled appearance of the abdomen ("prune belly") and explains the marked bulging of the flank contours shown on the abdominal radiograph.
Urinary tract abnormalities include:
1) Bilateral hydroureteronephrosis, often with extremely dilated, tortuous ureters
2) Varying degrees of renal dysplasia
3) Enlarged urinary bladder, often with urachal diverticulum
4) Vesicoureteral reflux is common
5) Poor contractility of the bladder
6) Dilated posterior urethra without urethral obstruction
Prune-belly syndrome occurs with variable degrees of severity. In severe cases, renal dysplasia and oligohydramnios in utero results in pulmonary hypoplasia; these infants may be stillborn or die shortly after birth often due to respiratory complications. Those who survive infancy have less severe renal disease but may have recurrent urinary tract infection or progressive renal insufficiency. Some mild cases may have little or no loss of renal function and therefore a better prognosis.
This infant was diagnosed with hydronephrosis on a prenatal ultrasound. The major differential diagnosis of bilateral hydroureteronephrosis in a male infant includes:
1) posterior urethral valves
2) severe bilateral vesicoureteral reflux
Whereas these two entities require a voiding cystourethrogram for diagnosis, the clinically obvious absence of abdominal musculature in Prune-belly syndrome suffices to confirm the malformation. Ultrasound examination may then be used to determine the severity of hydroureteronephrosis, estimate renal dysplasia and bladder dilatation and provide a baseline for follow up.
Ultrasound examination of this infant demonstrates the typical sonographic appearance of the urinary tract in Prune-belly syndrome: