Prune-belly syndrome is characterized by the following three findings: lack of abdominal muscles, undescended testes, and abnormal development of the urinary tract. Also known as Eagle-Barrett syndrome, this rare disorder was first described in 1839.
Prune-belly syndrome displays a wide range of severity. Affected individuals will have little to no muscle in their abdominal wall. The abdomen will appear wrinkled, like a prune. In male infants, the testicles, although present, are usually not seen. They remain inside the infant's abdomen. They fail to move to the normal position during development of the fetus. Undescended testesare a risk factor for infertility and testicular cancer later in the infant's life.
There are a variety of urinary tract abnormalities that occur in this syndrome. The kidneys may not form fully, and the level of development of the kidneys varies. The ureters, the tubes that connect the kidneys to the bladder, may be very large. In the portions that are very large, the urine may not be able to flow as well as normal. The bladder, the organ that holds the urine, may also be very large. A connection between the umbilicus and bladder may be present as well. The urethra may have areas that are very dilated and others that are very narrow. The narrowing may not allow the urine to flow out well. This blockage causes the bladder to become very large. The drainage of the fetus' bladder is what makes up the amniotic fluid during pregnancy. If the bladder cannot be drained, then not enough amniotic fluid will be present. The lack of amniotic fluid, or oligohydramnios, can cause poor formation of the fetus' lungs. The bladder in these patients may become so large that a mass can be seen and felt on the baby.
Ten percent of cases may have various abnormalities of the heart or large blood vessels. A percentage of cases will have abnormalities of their musculoskeletal system such as: dislocation of the hips, abnormal indentation of their chest, malformed feet or fingers, and a spine that is not aligned properly.
A specific genetic defect is unknown. Multiple cases in families are rare but have been reported. The risk of recurrence in future pregnancies is unknown but is thought to be low.
Despite the lack of a specific genetic defect or pattern of inheritance , over 95% of affected individuals are male. The incidence of this syndrome is estimated at one in 40,000 births.
Signs and symptoms
There are many symptoms that infants may experience in the newborn period. Most of these depend on the extent of damage that exists in the lungs and urinary tract. Infants who have poorly developed lungs, may be unable to breathe on their own at birth. They may also develop a collapsed lung or pneumothorax. If the infant does not have a normal rib cage then their ability to move air into and out of their lungs is impaired. This can lead to infections in the lung.
Since infants may not be able to eliminate of all their urine, they are at risk of having repeated urinary tract infections.
At birth, the syndrome is easily diagnosed based on the three findings that have been described. There is no specific prenatal or genetic test that can diagnose prune-belly syndrome. The diagnosis of prune-belly syndrome can be made in the prenatal period by ultrasound. Ultrasound can show some of the findings in this syndrome such as: distended bladder and ureters, oligohydramnios, and cryptorchidism. An enlarged bladder can be seen in other syndromes besides prune-belly, however, these findings on ultrasound should alert a physician to prune-belly as a possible cause.
Treatment and management
The potential treatments for prune-belly syndrome depend upon whether the diagnosis is made at birth or in utero. It also varies depending upon how severe the abnormalities are. Over the past two decades, different surgical procedures have been performed on fetuses in an attempt to correct the urinary tract obstructions that occur. One of these procedures is the vesicoamniotic shunt. This procedure relieves bladder obstructions by placing a tube in the fetal bladder allowing amniotic fluid to be produced as usual. The production of amniotic fluid allows for normal development of the lungs. There is not much information regarding the long-term outcomes for persons who receive these shunts. In infants who survive but have renal failure , kidney transplantation has been attempted with some success.
Approximately 20% of patients with this syndrome are stillborn. Thirty percent of infants do not survive past two years due to renal failure or infection. The remaining 50% of the infants will have a variety of urinary tract problems. A recent study looked at what factors may predict which children with prune-belly syndrome will develop renal failure. In this study, 35 patients with prune-belly syndrome between 1960 and 1997 were examined. Developing pyelonephritis (infection and inflammation of the kidney) at some point in time, having an elevated baseline creatinine, and having both kidneys look abnormal on an ultrasound were predictive for developing renal failure.
Behrman, Richard, et al. "Prune-Belly Syndrome." In NelsonTextbook of Pediatrics. Philadelphia: W.B. Saunders Company, 2000.
Freedman, A.L., et al. "Long-term outcome in children after antenatal intervention for obstructive uropathies." The Lancet 354 (July 1999): 374–7.
Leeners, B., et al. "Prune-Belly Syndrome: Therapeutic Options Including In Utero Placement of a Vesicoamniotic Shunt." Journal of Clinical Ultrasound 28, no. 9 (November/December 2000): 500–7.
National Organization for Rare Disorders (NORD). PO Box 8923, New Fairfield, CT 06812-8923. (203) 746-6518 or (800) 999-6673. Fax: (203) 746-6481. <http://www.rarediseases.org>.
Online Mendelian Inheritance in Man (OMIM). <http://www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?100100>.
David Elihu Greenberg, MD