eMedicine Specialties > Radiology > Pediatrics
Prune Belly Syndrome
Updated: Oct 2, 2009
Introduction
Background
Prune belly syndrome typically occurs in boys with a thin or lax abdominal wall; such laxity is variable in severity. The prostatic urethra is long and dilated as a result of prostatic hypoplasia. Some patients have a utricle diverticulum from the urethra; a large, vertically oriented, thick-walled bladder; a urachal remnant from the dome of the bladder; and tortuous and dilated ureters. Varying amounts of hydronephrosis and varying degrees of renal dysplasia are seen. All have cryptorchidism.
The amniotic fluid volume may be normal or decreased in neonates with prune belly syndrome. The presence of oligohydramnios may account for some of the accompanying findings of the extremities.[1,2,3 ]
The abdomen of an infant with prune belly syndrome shows marked distention of the abdomen and bulging flanks secondary to a large urinary system and the absence of abdominal wall musculature.
Ultrasound examination of the kidneys shows bilateral hyperechoic kidneys with poor development of the calyces and dilated tortuous ureters.
On CT, the ureter in this patient with prune belly syndrome fills the entire abdomen.
Recent cases and studies
Siebert and Walker reported on the recurrence of urethral stenosis/atresia in 2 sibling fetuses with bladder outlet obstruction, severe oligohydramnios, pulmonary hypoplasia, and prune belly syndrome (ie, stretching and eventually hypoplasia or even absence of abdominal muscles). A microdeletion of 6p25.3 was identified in the mother and one fetus, but the authors noted that it is not associated with a gene known to be involved in urethral development and was therefore of unknown significance.[4 ]
Laborie et al investigated a family, including one twin, with transient neonatal diabetes and prune belly sequence. According to the authors, their findings suggested that the loss of methylation on chromosome 6q24 and elsewhere may indicate a generalized maternal hypomethylation syndrome, which may account for both transient neonatal diabetes and prune belly sequence. The proband had loss of methylation at the 6q24 locus TNDM and also at the loci IGF2R, DIRAS3, and PEG1, while the other family members, including the healthy monozygotic twin, had normal findings.[5 ]
Leeners et al reported on 4 cases of prune belly syndrome diagnosed by prenatal ultrasonography. In 2 cases, the pregnancies were terminated because of a poor prognosis on the basis of ultrasound and laboratory findings. In one of the other 2 cases, vesicoamniotic shunt therapy was not performed because of a twin pregnancy, and the neonate died the day of delivery (by cesarean section at 31 weeks' gestation). In the fourth case, vesicoamniotic shunt therapy was successfully performed, and a healthy child was delivered. The authors noted that several conditions must be met for vesicoamniotic shunt therapy to have a good chance of success in fetal prune belly syndrome: the karyotype must be normal, other malformations must be excluded by ultrasonography, and renal function must be normal, as determined by serial analyses of fetal urine. Generally, the shunt should be inserted as early as possible.[6 ]
Pathophysiology
The etiology of prune belly syndrome is not fully understood. The thinness of the abdominal wall has been attributed to hydronephrosis. The distended urinary system is thought to interfere with the normal descent of the testes. However, some patients with severe hydronephrosis do not have the same disorder of the abdominal wall. Cryptorchidism usually is not seen in patients with distended bladders of other etiology.[7,8 ]
Frequency
United States
Prune belly syndrome is a rare anomaly seen in 1 in 35,000-50,000 live births. The genetic origins remain unclear.[9,4,5 ]
Mortality/Morbidity
Controversy exists concerning the management of prune belly syndrome. Management may consist of aggressive surgical repair involving tapering of the ureters and reimplantation, or surgical intervention may not be employed. An ideal approach has not been established; this is not surprising, given the varying degrees of clinical severity. Morbidity relates to the urinary tract; poor ureteral peristalsis and weak forward propulsion of urine in the ureters result in stasis, infection, and stone formation. Renal failure results from underlying renal dysplasia and the aforementioned complications of urinary stasis.
In the 1970s, half of the patients with prune belly syndrome died in early infancy. The survival rate has improved markedly. The severe abdominal distention is associated with pulmonary hypoplasia that is related to the patient's large abdominal content and compromise of the thorax during fetal development.
Race
Prune belly syndrome occurs in individuals of all races.
Sex
Prune belly syndrome occurs almost exclusively in males; less than 3% of cases of prune belly syndrome involve female patients.
In both genders, prune belly syndrome involves the abdominal wall, bladder, ureters, and kidneys. No urethral anomalies are seen in females. Males often demonstrate abnormality of the posterior urethra, resulting from abnormality of the posterior lobe of the prostate. Males occasionally also have nondevelopment of the corpora of the phallus.
Age
The diagnosis of prune belly syndrome is made in utero using ultrasound (US). In the neonate, the diagnosis is made on the basis of characteristic clinical findings. The diagnosis should be suspected in the fetus when US imaging reveals a characteristic enlarged bladder, dilated ureters, and an abnormal abdominal wall. However, the same constellation of US findings can signal posterior urethral valves with severe hydroureteronephrosis; thus, as a cautionary measure, the diagnosis should not be declared with certainty for either condition.
Occasionally, prune belly syndrome is reported in adults presenting with hypertension secondary to renal disease.
Anatomy
Abdominal wall
The abdominal wall defect in prune belly syndrome varies from a complete absence of musculature and scanty subcutaneous tissue to an abdomen with an apparently normal appearance. The lower portion of the abdomen usually is involved, and the flanks bulge. The margins of the liver and spleen, as well as bowel loops, are visible. The chest appears small with flaring of the lower ribs. The wrinkled appearance of the dystrophic abdominal wall is responsible for the prunelike appearance of the abdomen.
Urethra
The urethra may be normal, or portions of the corpus spongiosum may be absent; such absence is associated with megalourethra of the anterior urethra. The posterior urethra is elongated and dilated. It has a funnel-shaped appearance that resembles a posterior urethral valve; however, the presence of a valve is unusual in prune belly syndrome.
A persistent prostatic utricle usually is present in the posterior urethra at the verumontanum. Underdevelopment of the posterior lobe of the prostate gland results in a diverticulum-like posterior projection of the posterior portion of the urethra. The appearance is that of a prostatic utricle.
Bladder and urachus
The bladder in prune belly syndrome is large, vertical in orientation, and often thick-walled. In some patients, a bulging conical dome of the bladder represents persistent urachus. The bladder usually is distended at the trigonal region. Vesicoureteral reflux often occurs. A large postvoid residual volume is also a frequent occurrence.
Ureters
The ureters are markedly tortuous and dilated, with the distal ureter more affected than the proximal ureter. The wall of the ureter is fibrous, with deletion of the muscular layer. Ureteral function may at times improve with tapering.
Kidneys
Dilatation of the renal pelves with clubbing of the renal calyces and a diminished number of calyces is characteristic. The kidneys are hypodysplastic, often with diffuse parenchymal cysts. The degree of renal dysplasia does not correlate with the involvement of the abdominal wall or of hydronephrosis. Progressive renal failure occurs with repeated infection.
Testes
All male patients with prune belly syndrome have cryptorchidism. The testes are present; they are usually small and are located intra-abdominally. Whether the condition of nondescent represents a primary defect in relation to the absence of abdominal wall musculature is unknown. Sperm usually are absent. Neoplasia has been reported to occur in the testes.
Associated abnormality
In the GI tract, anomalies include malrotation with mesenteric defect, imperforate anus, gastroschisis, Hirschsprung disease, and constipation.[10 ]
Cardiac
Cardiac anomalies in prune belly syndrome include ventriculoseptal defect and atrial septal defect; such defects have been reported in 10% of patients.
Pulmonary
Pulmonary anomalies include hypoplasia resulting from the oligohydramnios, compression from the large abdomen, and Potter syndrome (pneumothorax, pneumomediastinum). Respiratory compromise secondary to abdominal muscular deficiency may be seen. Pneumonia and atelectasis also are observed occasionally.
Extremities
Skin dimples over the joints are seen in patients with prune belly syndrome. Lower-extremity deficiencies are also seen; such deficiencies include clubfoot and developmental dysplasia of the hip, which occurs as a result of fetal crowding by oligohydramnios.
Presentation
See Anatomy.
Preferred Examination
To confirm prune belly syndrome, radiography is used to evaluate the abdomen and chest initially. For urinary tract evaluation, renal US and voiding cystourethrography are performed. For fragile neonates and for infants with severe reflux and retention, these simple diagnostic studies may be much more threatening than they are for the normal baby. The use of prophylactic antibiotics and the need to act upon the study results should be weighed before proceeding indiscriminately.
Some diagnosticians assess renal function by performing a technetium-99m (99m Tc) dimethylsuccinic acid (DMSA) renal scan. DMSA is a cortical agent; DMSA renal scans provide information about both the appearance and function of the kidneys.
Differential Diagnoses
Posterior Urethral Valve
Pulmonary Hypoplasia
Other Problems to Be Considered
Megacystis microcolon
Intestinal hypoperistalsis syndrome
Severe bilateral vesicoureteral reflux
Detrusor-sphincter dyssynergia
Neurogenic bladder
Radiography
Findings
Radiographic findings in prune belly syndrome are as follows:
- Chest: Hypoplastic lungs, flaring of the lower ribs secondary to the distended abdomen is seen (see Image below and Image 2 in Multimedia).
Note the small lung volumes and constriction of the upper thorax. Flaring of the lower ribs secondary to distention of the abdomen is seen. Infants with prune belly syndrome may develop severe respiratory distress secondary to the thoracic limitation.
- Abdomen: Diffusely distended flanks are seen. Masslike areas in the abdomen represent a hydronephrotic urinary tract (see Image below and Image 1 in Multimedia).
The abdomen of an infant with prune belly syndrome shows marked distention of the abdomen and bulging flanks secondary to a large urinary system and the absence of abdominal wall musculature.
- Kidneys: Dilated, clubbed, and dysplastic calyces are seen. Renal parenchyma often is hyperechoic on US, which shows poor development and differentiation of the calyces. Often, small cysts are seen in the subcapsular cortex.
- Ureters: Ureters are markedly dilated and tortuous, with involvement more severe distally. Usually, refluxing ureters are seen (see Image below and Image 7 in Multimedia).
Infants with prune belly syndrome show early and marked bilateral vesicoureteral reflux. Significantly more dilatation of the lower ureters exists.
- Bladder: The bladder is vertical and trabeculated, with a urachal remnant at the dome. The base of the bladder is triangular, with a relaxed internal sphincter (see Image below and Image 8 in Multimedia).
A characteristic bladder in prune belly syndrome with vertical orientation, wide trigone, and a urachal remnant. The urethra shows elongation of the posterior urethra with a triangular deformity of the prostatic urethra related to the absent posterior lobe of the prostate.
- Urethra: A wide, long posterior urethra is seen, along with a utricular remnant. The posterior urethra may be triangular in appearance as a result of the absence of the posterior lobe of the prostate. Corporal absence may result in megalourethra of the anterior urethra, giving it a fusiform appearance (see Image below and Image 9 in Multimedia).
Typical urethra of prune belly syndrome
- Cryptorchidism: The testes are in the abdomen or inguinal canals. Often, the testes appear hypoplastic, although they may be of normal size.
For those who have access to nuclear radiology, a scan using a cortical agent such as99m Tc DMSA is useful in assessing renal function. Radiopharmaceuticals that are excreted by tubular secretion such as99m Tc mercaptoacetyltriglycerine (MAG-3) or glomerular filtration such as diethylenetriamine pentaacetic acid (DTPA) may be helpful in visualizing the kidneys and collecting systems.
Degree of Confidence
The radiographic appearance is virtually always characteristic of prune belly syndrome.
Computed Tomography
Findings
On CT, the ureter in this patient with prune belly syndrome fills the entire abdomen.
Findings of prune belly syndrome on CT include a broad flabby-appearing abdomen, absence of the musculature of the abdomen, hydronephrosis, and tortuous dilated ureters and bladder (see Image above and Image 6 in Multimedia).
Ultrasonography
Findings
Ultrasound examination of the kidneys shows bilateral hyperechoic kidneys with poor development of the calyces and dilated tortuous ureters.
High-detail sonogram of an involved kidney shows a hyperechoic cortex, a dysplastic collecting system, and cortical cysts.
In prune belly syndrome, an abdominal sonogram usually shows dilated ureters filling the entire abdomen.
Note the dilated and hypotonic ureters filling the abdomen in an infant with prune belly syndrome.
Sonography of the kidneys shows diffusely hyperechoic parenchyma, small parenchymal cysts, clubbed dysplastic calyces, and markedly tortuous ureters; these findings are sufficient to make the diagnosis of prune belly syndrome. The increased echogenicity of the parenchyma is an indicator of underlying dysplasia of the renal tissue during early differentiation and maturation. The bladder is usually large and thick-walled. Angled outlet views may show the dilated prostatic urethra, which is difficult to differentiate from posterior urethral valves by sonography alone[11,12,13 ](see Images above and Images 3-5, Image 10 in Multimedia).
Degree of Confidence
On US, prune belly syndrome has a characteristic appearance.
Although a firm diagnosis may usually be made on the basis of the combination of the clinical examination and US findings, in cases in which abdominal thinning is mild, the diagnosis may be less certain. In such cases, a voiding cystourethrogram may reveal the characteristic urethral appearance.
False Positives/Negatives
Megacystis-microcolon syndrome may have an appearance that is almost identical to that of prune belly syndrome; however, in megacystis-microcolon syndrome, the bladder is smoother and larger than in prune belly syndrome. Megacystis-microcolon syndrome has a marked female preponderance.
Nuclear Imaging
Findings
Renal cortical scanning is extremely useful for infants with borderline renal function. DMSA renal scanning indicates the degree of renal functional impairment and demonstrates focal areas of decreased or absent function.
Intervention
Nonoperative management: Because there is no clear evidence indicating that reconstructive surgery improves function for patients with prune belly syndrome, some patients do well without reconstruction, provided freedom from infection is maintained.
Surgery is indicated to repair cryptorchidism.
For urinary drainage, vesicostomy is used in patients with severe reflux who have an inability to empty the bladder. Reconstruction of the urinary tract with tapering and reimplantation of the ureters is undertaken in the more severely affected infants or as a staged procedure in children; it is beneficial in decreasing the urinary stasis that occurs in severely affected patients.
Despite extensive attempts to drain urine adequately, children with prune belly syndrome may develop renal failure.[6,14,15,16 ]
Multimedia
Media file 1: The abdomen of an infant with prune belly syndrome shows marked distention of the abdomen and bulging flanks secondary to a large urinary system and the absence of abdominal wall musculature.
Media file 2: Note the small lung volumes and constriction of the upper thorax. Flaring of the lower ribs secondary to distention of the abdomen is seen. Infants with prune belly syndrome may develop severe respiratory distress secondary to the thoracic limitation.
Media file 3: Ultrasound examination of the kidneys shows bilateral hyperechoic kidneys with poor development of the calyces and dilated tortuous ureters.
Media file 4: High-detail sonogram of an involved kidney shows a hyperechoic cortex, a dysplastic collecting system, and cortical cysts.
Media file 5: In prune belly syndrome, an abdominal sonogram usually shows dilated ureters filling the entire abdomen.
Media file 6: On CT, the ureter in this patient with prune belly syndrome fills the entire abdomen.
Media file 7: Infants with prune belly syndrome show early and marked bilateral vesicoureteral reflux. Significantly more dilatation of the lower ureters exists.
Media file 8: A characteristic bladder in prune belly syndrome with vertical orientation, wide trigone, and a urachal remnant. The urethra shows elongation of the posterior urethra with a triangular deformity of the prostatic urethra related to the absent posterior lobe of the prostate.
Media file 9: Typical urethra of prune belly syndrome
Media file 10: Note the dilated and hypotonic ureters filling the abdomen in an infant with prune belly syndrome.
Media file 11: Both prebirth and postnatally, the motion of the diaphragm is restricted by the large size of the abdomen. Because of this effect, most infants with prune belly syndrome have hypoplastic lungs.
References
Eagle JF, Barrett GS. Congenital deficiency of abdominal musculature with associated genitourinary abnormalities: A syndrome. Report of 9 cases. Pediatrics. Nov 1950;6(5):721-36. [Medline].
Wakhlu AK, Wakhlu A, Tandon RK, Kureel SN. Congenital megalourethra. J Pediatr Surg. Mar 1996;31(3):441-3. [Medline].
Woods AG, Brandon DH. Prune belly syndrome. A focused physical assessment. Adv Neonatal Care. Jun 2007;7(3):132-43; quiz 144-5. [Medline].
Siebert JR, Walker MP. Familial recurrence of urethral stenosis/atresia. Birth Defects Res A Clin Mol Teratol. Aug 2009;85(8):715-9. [Medline].
Laborie LB, Mackay DJ, Temple IK, Molven A, Søvik O, Njølstad PR. DNA hypomethylation, transient neonatal diabetes, and prune belly sequence in one of two identical twins. Eur J Pediatr. Jun 13 2009;[Medline].
Leeners B, Sauer I, Schefels J, et al. Prune-belly syndrome: therapeutic options including in utero placement of a vesicoamniotic shunt. J Clin Ultrasound. Nov-Dec 2000;28(9):500-7. [Medline].
Wheatley JM, Stephens FD, Hutson JM. Prune-belly syndrome: ongoing controversies regarding pathogenesis and management. Semin Pediatr Surg. May 1996;5(2):95-106. [Medline].
Woolf AS, Thiruchelvam N. Congenital obstructive uropathy: its origin and contribution to end-stage renal disease in children. Adv Ren Replace Ther. Jul 2001;8(3):157-63. [Medline].
Kupferman JC, Druschel CM, Kupchik GS. Increased prevalence of renal and urinary tract anomalies in children with Down Syndrome. Pediatrics. Sep 14 2009;[Medline].
Vemulakonda VM, Kopp RP, Sorensen MD, Grady RW. Recurrent nephrogenic adenoma in a 10-year-old boy with prune belly syndrome : a case presentation. Pediatr Surg Int. May 2008;24(5):605-7. [Medline].
Cromie WJ. Implications of antenatal ultrasound screening in the incidence of major genitourinary malformations. Semin Pediatr Surg. Nov 2001;10(4):204-11. [Medline].
Kaefer M, Peters CA, Retik AB, Benacerraf BB. Increased renal echogenicity: a sonographic sign for differentiating between obstructive and nonobstructive etiologies of in utero bladder distension. J Urol. Sep 1997;158(3 Pt 2):1026-9. [Medline].
Weiner Z, Goldstein I, Bombard A, Applewhite L, Itzkovits-Eldor J. Screening for structural fetal anomalies during the nuchal translucency ultrasound examination. Am J Obstet Gynecol. Aug 2007;197(2):181.e1-5. [Medline].
Noh PH, Cooper CS, Winkler AC, et al. Prognostic factors for long-term renal function in boys with the prune-belly syndrome. J Urol. Oct 1999;162(4):1399-401. [Medline].
Saxena AK, Brinkmann OA. Unique features of prune belly syndrome in laparoscopic surgery. J Am Coll Surg. Aug 2007;205(2):217-21. [Medline].
Levine E, Taub PJ, Franco I. Laparoscopic-assisted abdominal wall reconstruction in prune-belly syndrome. Ann Plast Surg. Feb 2007;58(2):162-5. [Medline].
Keywords
prune belly syndrome, congenital absence of abdominal musculature, deficiency of abdominal musculature, Eagle-Barrett syndrome, triad syndrome
Contributor Information and Disclosures
Author
Beverly P Wood, MD, PhD, Professor Emerita, Departments of Radiology and Pediatrics, Division of Medical Education, Keck School of Medicine, University of Southern California; Professor of Clinical Radiology, Loma Linda University School of Medicine
Beverly P Wood, MD, PhD is a member of the following medical societies: American Academy of Pediatrics, American Association for Women Radiologists, American College of Radiology, American Institute of Ultrasound in Medicine, American Medical Association, American Roentgen Ray Society, Association of University Radiologists, Radiological Society of North America, and Society for Pediatric Radiology
Disclosure: Nothing to disclose.
Medical Editor
Robert J Starshak, MD, Medical Director, Assistant Clinical Professor, Department of Radiology, Medical College of Wisconsin, Falls Medical Group
Disclosure: Nothing to disclose.
Pharmacy Editor
Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.
CME Editor
Robert M Krasny, MD, Resolution Imaging Medical Corporation
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.
Chief Editor
John Karani, MBBS, FRCR, Clinical Director of Radiology and Consultant Radiologist, Department of Radiology, King's College Hospital, London
John Karani, MBBS, FRCR is a member of the following medical societies: British Institute of Radiology, British Society of Interventional Radiology, Cardiovascular and Interventional Radiological Society of Europe, European Society of Gastrointestinal and Abdominal Radiology, European Society of Radiology, Radiological Society of North America, and Royal College of Radiologists
Disclosure: Nothing to disclose.