Prune belly syndrome (PBS), also known as triad syndrome, is a birth disorder that combines three birth defects. The muscles of the abdomen are either missing altogether or partially developed, the urinary tract is not properly formed and in male infants one or both of the testicles does not descend into the scrotal sac.
Prune belly syndrome gets it’s name from the wrinkled, prune-like appearance of the skin on the stomach of the patient. It is also known by other names such as:
- Abdominal Muscle Deficiency Syndrome
- Congenital Absence of the Abdominal Muscles
- Eagle-Barrett Syndrome
- Obrinsky Syndrome
- Triad Syndrome
- Urethral Obstruction Malformation Sequence
- Deficiency of Abdominal Musculature
What Causes Prune Belly Syndrome?
There is no identifiable cause for prune belly syndrome. However, researchers have several theories and continued research is required to figure out which theory is accurate.
Currently, we know that male infants are far more susceptible to the disorder than females. Some researchers believe that the bladder of the fetus has an abnormality to accumulate large amount of urine, which causes the distending of the bladder, ureters and kidney.
This theory suggests that the expanding bladder causes abdominal muscles problems in proper fetal development. The obstruction of the enlarged bladder also prevents the testes from descending and may cause the urinary tract malformation. By the time the fetus is ready for birth, the urethral obstruction may be removed, with no identifiable cause for the triad condition.
A second theory suggests that improper development of the abdominal muscles leads to the abnormal function of the bladder. Research supporting this theory suggests that incomplete development of abdominal muscles also causes the bladder to retain urine, which may leading to infections and malformation of organs. They also link improper development of chest muscles and respiratory problems to the disorder.
Research is currently being undertaken to prove either of these theories, or suggest alternatives. It is also possible that the improper muscular development and urinary tract disorders have another cause, such as a nervous system defect that causes malfunctioning of the muscles.
Siblings often suffer from the disorder, suggesting a genetic link. Since a number of other genetic disorders have been linked with prune belly syndrome, there may even be an inheritance pattern which we are unaware of.
The degree of severity of prune belly syndrome varies from case to case. Possible symptoms of the syndrome that may help in the the diagnosis include:
- Absent abdominal muscles, or partially formed abdominal muscles
- Poorly developed chest muscles
- Cryptorchidism or undescended testicles in boys
- Enlarged bladder
- Enlarged kidney or hydronephrosis
- Urinary tract problem such as blocked ureters or enlarged ureters
- Blood or pus in the urine
- Gastrointestinal anomalies
- Club foot
- Congenital heart disease
- Spinal cord malformations
- Malformation of external genitalia in girls
Not all symptoms need to be present for the birth defect to afflict the child.
Physical signs on the body include the wrinkled appearance of the skin on the belly resembling a prune. There may be a swelling visible where the enlarged bladder pokes through, making it look like a lump in the abdominal region.
Peristalsis, or the involuntary constriction and relaxation of the intestinal muscles as they push food through the digestive tract, can also be easily seen in a child with prune belly syndrome. The wave-like muscle contractions are obvious in the abdominal region.
Affected children may have problems sitting up straight due to the poorly developed abdominal muscles. There may also be a problem in the child’s ability to move around.
Urinary tract infections are common in children with PBS, as the ureters are often blocked when the bladder gets enlarged. This allows urine to collect for much longer periods of time in the body and bacterial infections grow.
Reviewed by Yolanda Smith, BPharm