Bladder, ureter & renal pelvis

Congenital anomalies

Prune belly syndrome

Last author update: 1 August 2016
Last staff update: 12 November 2021

Copyright: 2002-2023,, Inc.

PubMed Search: pediatric prune belly syndrome

Erdener Özer, M.D., Ph.D.
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Cite this page: Özer E. Prune belly syndrome. website. Accessed September 28th, 2023.
Definition / general
  • Prune belly syndrome (PBS) is a congenital disorder of the urinary system with renal, ureteral and urethral abnormalities
  • The syndrome is named for the mass of wrinkled abdominal skin often present
  • First described in 1839 by Frölich, but Osler gave the condition its name (Pediatr Surg Int.2012;28:219)
Essential features
  • The three phenotypic features of the classical triad are:
    • Urinary tract malformations such as unusually large ureters (megaureter), distended bladder (megacystitis), vesicoureteral reflux
    • Partial or complete absence of the abdominal muscles
    • Bilateral cryptorchidism
  • Abdominal Muscle Deficiency Syndrome, Congenital Absence of the Abdominal Muscles, Eagle-Barrett Syndrome, Obrinsky Syndrome, Fröhlich Syndrome, Triad Syndrome
  • Rare, genetic birth defect affecting about 1 in 40,000 births
  • 97% male
  • Associated with twinning - 4% of all cases are products of twin pregnancies
  • Associated with trisomy 18 and 21
  • Reference: Fetal Pediatr Pathol 2013;31:13
  • The prevailing theory is mesodermal arrest, which explains the involvement of the genitourinary tract, testis and abdominal wall (J Urol 1994;152:2328); a noxious insult would have to occur between gestational weeks 6 and 10
  • The distended bladder could result in the abnormal development of the abdominal wall musculature and prevent the descent of the testis
  • Autosomal dominant or X linked recessive inheritance has been suggested in some cases
  • A homozygous mutation in the muscarinic cholinergic receptor 3 gene (CHRM3) on chromosome 1q43 was reported in one family
Clinical features
  • A partial or complete lack of abdominal wall muscles
  • Urinary tract abnormality such as unusually large ureters, distended bladder or vesicoureteral reflux due to obstruction; the site of obstruction may be as high as the pelviureteral junction or as low as the prostatic membranous urethra
  • Cryptorchidism (undescended testicles)
  • Frequent urinary tract infections
  • Ventricular septal defect, tetralogy of Fallot
  • Musculoskeletal abnormalities include pectus excavatum, scoliosis and congenital joint dislocations including the hip
  • Others: renal dysplasia, constipation, increased pulmonary secretions, malrotation of the gut, club foot, post-ejaculatory discomfort
  • Reference: Urology 2015;85:211
  • PBS can be diagnosed via ultrasound in utero based on an abnormally large abdominal cavity due to accumulated urine
  • A rise in BUN and creatinine levels associated with decreased urine output indicates urinary obstruction in the neonate
  • In young children, frequent urinary tract infections, typically uncommon, often herald PBS; diagnosis is suggested by a voiding cystourethrogram
  • Diagnosis necessitates a thorough orthopaedic evaluation because of the high prevalence of associated musculoskeletal abnormalities
Radiology description
  • Renal and bladder ultrasonography is recommended as early as possible to evaluate the urinary tract
  • Contrast voiding cystourethrography (VCUG) should be performed
Prognostic factors
  • PBS occurs with variable degrees of severity, with a mortality of 20%; with proper treatment, a longer, healthier life is possible
  • In severe cases, renal dysplasia and oligohydramnios in utero result in pulmonary hypoplasia; these infants may be stillborn or die shortly after birth due to respiratory complications
  • Those with less severe renal disease may survive infancy, but may have recurrent urinary tract infection or progressive renal insufficiency; some mild cases have little or no loss of renal function and therefore a better prognosis
  • Treatment depends on the severity of the symptoms (J Pediatr Urol 2015;11:276.e1)
  • Vesicostomy may prevent urinary tract infections
  • Consistent self-catheterization, often several times per day, may also prevent infections
  • A more drastic procedure is surgical "remodeling" of the abdominal wall and urinary tract
  • Boys often require orchiopexy
  • If renal failure develops, the child may need dialysis or a kidney transplant
Clinical images

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Gross images

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Swollen belly with
thin ventral wall
partially devoid
of muscle

Urethral obstruction sequence with megacystis

Distended bladder in postmortem examination

Differential diagnosis
  • For antenatal hydronephrosis with hydroureter, consider:
    • Posterior urethral valves: may show a keyhole sign and no evidence of cryptorchidism
    • Megacystis microcolon intestinal hypoperistalsis syndrome: tends to have polyhydramnios and more females affected
    • Pseudo-prune belly syndrome, which is associated with PBS uropathy, is characterized by normal abdominal wall examination findings and incomplete or absent cryptorchidism
    • An abdominal wall defect commonly confused with PBS has been termed prune belly-like variant
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