Prune belly syndrome

Prune belly syndrome


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.”


Although there was a single case reported in the literature diagnosed at 11 weeks based on a large abdominal cystic mass and abdominal distension, this condition is generally diagnosed after 20 weeks of gestation. The diagnosis should be considered when there is a massively distended abdomen and cryptorchidism in males, with or without obstructive uropathy. When there has been some resolution of the intraabdominal pressure, it may be possible to note the flaccid abdominal muscle tone. Ureterovesical junction (UVJ) and vesiculourethral reflux (VUR) are the most common obstructions noted. Megacystis and absence or agenesis of the urethra have also been seen as causes. Hydronephrosis, hydroureters, renal cystic dysplasia are also common. Anal atresia, lower limb hypoplasia or reduction anomalies of lower limbs may be caused by bladder distention leading to obstruction of the umbilical arteries. Approximately 10% of babies with PBS will also have cardiac malformations, most commonly ventricular septal and atrial septal defects and tetralogy of Fallot. Gastrointestinal anomalies can include malrotation of the gut, common mesentery, intestinal or anal atresia, gastroschisis or omphalocele. Spina bifida is also an occasional associated finding. In males, the prostate gland is usually hypoplastic, although the penis is normal. Affected females may have bicornuate or duplicated uterus, vaginal atresia, clitoral hypertrophy, and upper urinary tract anomalies.

Differential Diagnosis

Abdominal wall muscle atrophy or hypoplasia may be present as a different condition, without abnormal genitourinary findings. Obstructive uropathies may be present without the development of abdominal wall weakness. Prune belly” is primarily a descriptive term for the wrinkled, walnut like appearance of the abdomen. Megacolon associated with cystic fibrosis (meconium ileus) or Hirschsprung’s disease can cause significant abdominal distension without urinary tract involvement. Cystic or solid masses causing abdominal distension include ovarian cysts, hydrometrocolpos, infantile polycystic kidney disease, tumours such as Wilms tumour or neuroblastoma, but each will have organ-specific ultrasound findings. “

Sonographic Features

Large cystic abdominal structure with distension of the abdomen (in one case report identified by 11 weeks)

Flaccid” abdominal musculature demonstrated by easy depression of abdominal muscles when touched by fetal limb or palpated externally; this finding can only be seen when the internal pressure (ascites, etc) has been decompressed

Cryptorchidism in males

If caused by obstructive uropathy, there will be associated findings such as megacystis, hydroureter and/or hydronephrosis

Fetal ascites/hydrops may be present without signs of urinary tract obstruction”

Associated Syndromes

  • Familial prune belly
  • Microcystis- megacolon
  • Obstructical uropathies (VUR, PUV, UPJ)
  • OEIS (exstrophy of cloaca)
  • Trisomy 13
  • Trisomy 18
  • Turner


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