Discussion: Prune belly syndrome,
a congenital absence or hypoplasia of the anterior abdominal wall musculature, accompanied by a generalized dilatation of the urinary tract and bilateral cryptorchidism. The condition is also known as Eagle – Barrett or triad syndrome. The incidence is 1 in 35,000–50,000 live births. Prune belly syndrome occurs almost exclusively in males. The condition occurs sporadically, and the aetiology is unknown. A genetic predisposition has been proposed, and the occurrence of prune belly syndrome in siblings has been reported. Curiously, the condition is commoner in twin pregnancies. All reported twins have been discordant for the syndrome.
Clinically, neonates with prune belly syndrome are easily recognized by the appearance of the anterior abdominal wall, which is thin, lax, and wrinkled. The flanks often bulge markedly, with the thorax demonstrating secondary flaring at the cortal margins. While the abdominal wall defect is the most striking finding, the genitourinary tract abnormalities are the most serious. There is variable hydroureteronephrosis. Typically, the distal and midureter are more dilated than the proximal ureter, and the degree of hydronephrosis is usually less than would be expected from the degree of hydroureter. The renal parenchyma is usually preserved, but may demonstrate variable and asymmetric displasia. Generally the kidneys function well, but are prone to infection and resultant renal impairment. The bladder is typically large and dilated with an irregular thick wall. This does not appear to be due to detrusor hypertrophy, and urodynamics often show normal intravesical pressures. The posterior urethra may show variable dilatation. The anterior urethra is usually normal. Prenatally, oligohydramnios is common — probably due to the genitourinary abnormalities. This may result in pulmonary hypoplasia and orthopaedic problems such as club foot and congenital hip dislocation. Perinatal death may result from pulmonary hypoplasia, urosepsis, or renal failure.
Antenatal ultrasound (US) may suggest the diagnosis of prune belly syndrome, when hydroureteronephrosis with a large bladder and flaccid-appearing abdominal wall are detected. However, the prenatal distinction from severe vesicoureteric reflux or posterior urethral valves may be difficult. Postnatally, hydroureteronephrosis and bladder enlargement may be demonstrated by US, CT, MRI, or intravenous urography. Voiding cystourethrography typically shows a large bladder which empties slowly and incompletely. Vesicoureteric reflux is common (Fig.1). The prostatic urethra is often dilated, suggesting posterior urethral valves, but such valves are not present and in most cases, no clearly defined obstruction is present at the junction of the posterior and anterior urethras.
Many severely affected infants die in the perinatal period. The prognosis in other cases is reasonably good, provided adequate control of infection and reflux can be obtained. Urinary diversion may be required, because bladder and voiding dysfunction appears to contribute to progressive renal damage. Also see prune belly syndrome.
