Prune Belly Syndrome (PBS), also known as Eagle-Barrett Syndrome or triad syndrome, is a rare congenital disorder primarily affecting male infants. It is defined by a distinct set of three physical characteristics. The name originates from the newborn’s abdomen, which appears wrinkled and flabby, resembling a dried prune, due to underlying muscle deficiency. PBS is uncommon, occurring in an estimated one in 30,000 to 40,000 live births, with approximately 95% of cases diagnosed in males. Outcomes range from severe, life-threatening complications to a relatively normal lifespan.
The Defining Features of Prune Belly Syndrome
Prune Belly Syndrome is characterized by a specific clinical triad of features. The first feature is the partial or complete lack of musculature in the abdominal wall. This deficiency causes the abdominal skin to appear thin, loose, and wrinkled at birth, often resulting in a “pot-belly” appearance as the child grows.
The second component involves significant abnormalities of the urinary tract, including the bladder, ureters, and kidneys. The bladder is often abnormally large and distended (mega-bladder). The ureters, which connect the kidneys to the bladder, are typically enlarged and twisted (mega-ureter).
The third characteristic is bilateral cryptorchidism, the failure of both testicles to descend into the scrotum. In infants with PBS, the testicles remain in the abdomen. These three findings—the flabby abdomen, the malformed urinary tract, and the undescended testicles—constitute the diagnostic signature of the syndrome.
Etiology and Prenatal Detection
The exact cause of Prune Belly Syndrome remains largely unknown, and it is considered a sporadic developmental defect. One leading theory suggests that an obstruction in the urethra during early fetal development causes a massive buildup of urine. This leads to an enlarged bladder that secondarily causes the wasting of the abdominal muscles. Another hypothesis points to a defect in the lateral plate mesoderm, the primitive tissue layer that forms the urinary tract and abdominal wall.
While most cases appear random, the occurrence of the syndrome in siblings suggests an underlying genetic component may exist. Prenatal diagnosis is frequently accomplished through routine fetal ultrasound, often in the second trimester. The ultrasound can detect signs such as a distended bladder, dilated ureters, hydronephrosis (swelling of the kidneys), and the deficient abdominal wall. Severe cases may also present with oligohydramnios (an abnormally low volume of amniotic fluid), which indicates poor fetal urine production.
Critical Associated Health Complications
The anatomical defects defining Prune Belly Syndrome cause several secondary health complications. The urinary tract abnormalities, particularly the enlarged and poorly emptying bladder, lead to chronic urinary stasis. This inability to fully clear the bladder increases the risk of recurrent urinary tract infections (UTIs).
The chronic buildup of urine and the backflow of urine from the bladder into the ureters and kidneys, known as vesicoureteral reflux, causes progressive damage to the renal tissue. This sustained pressure and infection predispose patients to renal impairment. In 30% to 50% of cases, this can lead to end-stage renal disease. The severity of this renal dysplasia is the primary factor determining the long-term survival and prognosis.
The weak abdominal muscles impair the ability to cough forcefully, as these muscles are necessary for generating the required pressure. This compromised cough mechanism results in the retention of pulmonary secretions, making infants susceptible to recurrent respiratory infections and atelectasis (lung collapse). In severe cases, muscle deficiency and associated oligohydramnios contribute to pulmonary hypoplasia, which causes significant respiratory distress at birth.
Treatment Approaches and Long-Term Management
Treatment for Prune Belly Syndrome is individualized, depending on the severity of symptoms and renal involvement. Management begins with preventative medical strategies, such as continuous, low-dose antibiotic prophylaxis to reduce urinary tract infections and protect the kidneys. Due to the urinary tract malformations, children require lifelong monitoring by specialists, including urologists and nephrologists.
Surgical interventions address the primary features of the syndrome. An orchiopexy is performed to bring the undescended testicles down into the scrotum, typically before six months of age. Urologic surgeries may include a vesicostomy, which creates a temporary opening in the bladder through the abdomen to allow for continuous drainage of urine and improve bladder emptying.
Reconstructive surgery, such as abdominoplasty, may be performed to tighten the abdominal wall, improving mobility, posture, and respiratory function. For patients who develop end-stage renal disease, treatment shifts to renal replacement therapy, including dialysis or a kidney transplant. The long-term outlook is directly tied to kidney function; with timely care, many individuals with PBS can transition into adulthood.