Prune-Belly syndrome, also known as Eagle-Barrett syndrome, is a rare disorder characterized by partial or complete absence of the stomach (abdominal) muscles, failure of both testes to descend into the scrotum (bilateral cryptorchidism), and/or urinary tract malformations. The urinary malformations may include abnormal widening (dilation) of the tubes that bring urine to the bladder (ureters), accumulation of urine in the ureters (hydroureter) and the kidneys (hydronephrosis), and/or backflow of urine from the bladder into the ureters (vesicoureteral reflux). Complications associated with Prune-Belly syndrome may include underdevelopment of the lungs (pulmonary hypoplasia) and/or chronic renal failure. The exact cause of Prune-Belly syndrome is not known.
Prune Belly syndrome is characterized by partial absence of some or most abdominal muscles giving rise to a wrinkled or prune-like appearance. Often, the attachments of the muscles to the bones are present, but the muscles diminish in size and thickness over the bladder. The abdomen appears large and lax, the abdominal wall is thin and the intestinal loops can be seen through the thin abdominal wall. Skin folds may radiate from the navel or occur as transverse folds across the abdomen. A midline crease from the navel to pubic area may be present in some cases. The navel may appear as a vertical slit, or as a linear central scar, but it can also appear normal. Sometimes the navel is connected with the bladder through a canal (urachus) or a cyst. The chest is often deformed. Flaring of the rib margins or a horizontal depression under the chest (Harrison groove) can appear in many children born with Prune Belly Syndrome. Narrowing of the chest in the transverse direction (pigeon breast) may also occur.
Enlargement of the bladder is present in almost all cases. Obstruction of the neck of the bladder is the primary problem, resulting in bladder distention and urine retention. The connection between the kidney and bladder (ureter) may be abnormal; the opening between ureter and bladder may be narrowed or closed. Obstruction may also occur at the junction of the ureter and kidney. Usually, the ureters are greatly widened. Occasionally this enlargement occurs only on one side or decreases as the ureter nears the bladder. Distention of the kidney with urine (hydronephrosis), on one or both sides, may also occur. In some cases, hydronephrosis occurs on one side while the kidney is underdeveloped on the other side. Kidney cysts may also be present. The canal that carries urine from the bladder to the outside of the body (urethra) usually is unobstructed. In males, absence of an opening (atresia) in the urethra, folds acting as valves below the entrance of the semen and prostate ducts (verumontanum), compression by a pouch and overdevelopment of the prostatic urethra also have been noted in some cases.
Musculoskeletal abnormalities, especially club foot, are present in about 20% of cases, while cardiovascular abnormalities are seen in about 10% of cases.
Blood and pus in the urine (hematuria and pyuria) often signal infection. Undescended testes (cryptorchidism) and testes that may be attached to a ureter, often occur in males with Prune Belly syndrome. Abnormal fixation of the gastrointestinal tract and failure to rotate during fetal development (malrotation) have also been described in the medical literature.
The exact cause of Prune Belly syndrome is unknown. There are several theories.
It may be caused by an abnormality in the bladder during fetal development. Accumulation of urine can distend the bladder, the ureters, and the kidney. As the bladder enlarges, it causes wasting (atrophy) of the abdominal muscles. Retention of the testes in the abdomen (cryptorchidism) may be attributed to obstruction by an unusually large bladder or to obliteration of the groin (inguinal) canals. By the time of birth, the obstruction at the bladder outlet or the urethral obstruction may have been resolved, so that no mechanical obstacle can be identified after birth.
Other researchers consider the urinary abnormalities as secondary to the incomplete development of abdominal muscles. Incomplete emptying of the bladder leading to urinary retention and infection can occur as a result. Constipation and symptoms of indigestion are additional possible complications. Since the abdominal muscles are important for respiration, deformity of the chest could be explained by their absence.
A third possibility is that the muscle deficiency and the urinary abnormalities have a common cause that has not yet been discovered. A nervous system defect that could be responsible for early malfunction of abdominal muscles may be the cause. Association with a congenital open spinal canal (spina bifida) has been identified in some children, and the presence of clubfeet is also fairly commonly associated with Prune Belly syndrome.
Prune Belly syndrome is a very rare disorder that is present at birth. The disorder affects mostly males but a few female cases have been described in the medical literature.
The diagnosis is usually obvious from birth, but care and time are required to determine the location and number of abnormalities. A full understanding of the complications will involve imaging tests such as ultrasound, X-ray, and, in order to determine the extent of involvement of the genitourinary tract, intravenous pyelogram (IVP). An IVP makes use of a dye to map the degree of involvement of the kidneys and their ducts.
Treatment will depend upon the severity of the symptoms. Some children will require rather modest surgical procedures such as the creation of a small opening in the bladder through the abdomen (vesicostomy) that will facilitate voiding of urine, or a procedure to help the testicles descend into the scrotum (orchiopexy). More extensive surgical procedures such a. bladder reconstruction (cystoplasty), surgical widening of the urethra, and augmentation of the muscles that contract the bladder (detrusor augmentation) using a paired graft of a hip muscle (rectus femoris) have been successfully undertaken on children with prune belly syndrome. In rare cases, kidney transplantation may be necessary.
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