Prune belly syndrome

Description

Prune belly syndrome (PBS),also known as the Eagle-Barret syndrome, is a complex condition involving abnormalities of both the genitourinary tract and the abdominal wall musculature. It involves a triad of findings, including aplasia or hypoplasia of the abdominal wall musculature with abdominal distension; urinary tract obstruction or anomaly; cryptorchidism (in males). There are two current theories as to the aetiology of the muscle anomaly involved in this condition. One is that there is a common, early underlying cause for both the urinary tract and muscle abnormalities; the other is that the abdominal muscle hypotonia is caused by abdominal wall distension and is a secondary, deformation” result. In fact, both may be responsible for different cases. In the first theory, the embryological abnormality may be a disorganisation of the gastrointestinal musculature which leads to both hypoplasia of the abdominal muscles and pseudo-obstructive symptoms, where there may be no signs of structural obstruction. A mesodermal defect due to obstructed transition of myotomes from the lateral mesoderm to the lower abdomen between 4 and 5 weeks gestation may be the initial error. Abdominal muscle formation is usually completed by 5-12 weeks. In one case report, in a spontaneously aborted fetus at 12 weeks, muscle tissue anomalies could already be identified. The most common cause of PBS is obstructive uropathy. Abdominal muscle deficiency may develop secondary to increasing intra-abdominal pressure from enlarging bladder, ureters, and/or kidneys. Muscle atrophy may be due to ischemia and reduced nerve conduction because of the overextension of blood vessels and nerves, or due to overextension of abdominal wall muscles themselves. Bladder distension interferes with descent of testes leading to cryptorchidism. Urethral obstructions may also lead to oligohydramnios and pulmonary hypoplasia. Infants delivered with PBS and no obvious obstruction may have suffered an earlier transient obstructive event, such as transient ascites, a decompressed cyst or resolved megacystis. It is a rare condition, affecting 1/35,000 to 50,000 liveborn babies. Approximately 90% are male, presumably because males are more likely to suffer from obstructive uropathy. There is also an increased incidence in twins; about 1:23 twin pregnancies will be discordant for PBS. The prognosis is generally poor. Most perinatal and neonatal deaths are due to severe oligohydramnios and pulmonary hypoplasia. Survivors may develop pneumothorax or renal insufficiency. In less severe cases there still may be decreased renal function. Both cosmetic and functional problems arise from the abdominal muscle hypoplasia.”