AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Background

The child with prune belly syndrome typically is male with a thin or lax abdominal wall (variable in severity) and a long and dilated prostatic urethra from prostatic hypoplasia. Some 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.

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.

Pathophysiology

The etiology of prune belly syndrome is not fully understood. The thinned abdominal wall has been attributed to hydronephrosis and the distended urinary system to interfering with normal descent of the testes. However, other patients with severe hydronephrosis may not show the same abdominal wall disorder. Similarly, cryptorchidism usually is not seen with distended bladders of other etiology.

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.

Mortality/Morbidity

Controversy exists concerning the management of this entity, which ranges from aggressive surgical repair with tapering of the ureters and reimplantation to restraint from surgical intervention. An ideal approach has not been established, which is not surprising with such varying degrees of clinical severity. Morbidity relates to the urinary tract, in which poor ureteral peristalsis and weak forward propulsion of urine in the ureters results 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. Currently, the survival rate has improved markedly. The severe abdominal distention also is marked by pulmonary hypoplasia 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, with less than 3% of prune belly syndrome occurring in female patients.

Prune belly syndrome in both genders involves the abdominal wall, bladder, ureters, and kidneys. No urethral anomalies are seen in females, although males often demonstrate abnormality of the posterior urethra (resulting from abnormality of the posterior lobe of the prostate), and males occasionally also have nondevelopment of the corpora of the phallus.

Age

Diagnosis is made in utero using ultrasound (US) or in the neonate with characteristic clinical findings. Suspect the diagnosis 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 use caution not to declare with certainty either diagnosis.

Occasionally, prune belly syndrome is reported in adults presenting with hypertension secondary to renal disease.

Anatomy

Abdominal wall

The abdominal wall defect varies from a complete absence of musculature and scanty subcutaneous tissue to an apparently normal appearance of the abdomen. 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 and associated with megalourethra of the anterior urethra. The posterior urethra is elongated and dilated with 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 diverticulumlike posterior projection of the posterior portion of the urethra. The appearance is that of a prostatic utricle.

Bladder and urachus

The bladder 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, and large postvoid residual is frequent.

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 have cryptorchidism. The testes are present and usually are small and intra-abdominal in location. Whether the condition of nondescent represents a primary defect in relation to the absent abdominal wall musculature is unknown. Sperm usually are absent, and 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.

Cardiac

Anomalies include ventriculoseptal defect or atrial septal defect and 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 patient's joints and lower extremity deficiencies are sometimes seen, such as clubfoot and developmental dysplasia of the hip from fetal crowding by oligohydramnios.

Clinical Details

See Anatomy.

Preferred Examination

Use radiography to evaluate the abdomen and chest initially.

For urinary tract evaluation, perform renal US and voiding cystourethrography. In fragile neonates and infants who can be predicted to have severe reflux and retention, this simple diagnostic study may be much more threatening than in the usual 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 Tc 99m dimethylsuccinic acid (DMSA) renal scan; this is a cortical agent that shows both the appearance and function of the kidneys.

DIFFERENTIALS

Section 3 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Other Problems to be Considered

Megacystis microcolon
Intestinal hypoperistalsis syndrome
Severe bilateral vesicoureteral reflux
Detrusor-sphincter dyssynergia
Neurogenic bladder

RADIOGRAPH

Section 4 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

Radiographic findings are as follows:

• Chest: Hypoplastic lungs, flared lower ribs secondary to the distended abdomen are seen (see Image 2).
• Abdomen: Diffusely distended flanks are seen. Masslike areas in the abdomen represent a hydronephrotic urinary tract (see Image 1).
• Kidneys: Dilated, clubbed, and dysplastic calyces are seen. Renal parenchyma often is hyperechoic with US and shows poor development and differentiation of the calyces. Often, small cysts may be seen in the subcapsular cortex.
• Ureters: Ureters are markedly dilated and tortuous with involvement more severe distally. Usually, refluxing ureters are seen (see Image 7).
• 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 8).
• Urethra: A wide and long posterior urethra is seen with a utricular remnant. The posterior urethra may be triangular in appearance secondary to the absence of the posterior lobe of the prostate. Corporal absence can result in megalourethra of the anterior urethra, rendering it fusiform in appearance (see Image 9).
• Cryptorchidism: The testes are in the abdomen or inguinal canals. Often, the testes appear hypoplastic, although they may be normal size.

For those who have access to nuclear radiology, a scan using a cortical agent such as ^99mTc DMSA is of interest in assessing renal function. Radiopharmaceuticals that are excreted by tubular secretion such as ^99mTc mercaptoacetyltriglycerine (MAG-3) or glomerular filtration such as diethylenetriamine pentaacetic acid (DTPA) can be helpful in visualizing the kidneys and collecting systems.

Degree of Confidence

Radiographic appearance is so typical that it is virtually always characteristic of prune belly syndrome.

CT SCAN

Section 5 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

Findings on CT include a broad flabby-appearing abdomen, absence of the musculature of the abdomen, hydronephrosis, and tortuous dilated ureters and bladder (see Image 6).

ULTRASOUND

Section 6 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Findings

Sonography of the kidneys shows diffusely hyperechoic parenchyma, small parenchymal cysts, clubbed dysplastic calyces, and markedly tortuous ureters, which is sufficient to make the diagnosis. 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 that is difficult to differentiate from posterior urethral valves by sonography alone (see Images 3-5, Image 10).

Degree of Confidence

US has a characteristic appearance.

While the combination of the clinical examination and US may make the firm diagnosis, at times a mild degree of abdominal thinning may create doubt. The voiding cystourethrogram in those children can help when the characteristic urethral appearance is imaged.

False Positives/Negatives

Megacystis-microcolon syndrome may have an almost identical appearance; however, the bladder in patients with the latter is smoother and larger than in those with prune belly syndrome. Megacystis-microcolon syndrome has a marked female preponderance.

NUCLEAR MEDICINE

Section 7 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

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

Section 8 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

Nonoperative management: Since no clear evidence indicates that reconstructive surgery improves the function of these patients, some patients do well without reconstruction if freedom from infection is maintained.

Surgery to repair cryptorchidism is indicated.

For urinary drainage, vesicostomy is used in patients with severe reflux and 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 and appears to produce improvement by decreasing the urinary stasis that occurs in severely affected patients.

Despite extensive attempts to drain urine adequately, children may develop renal failure.

MULTIMEDIA

Section 9 of 10  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

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.
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Media file 2:  Note the chest with small lung volumes and constriction of the upper thorax, while flaring of the lower ribs is seen secondary to the distended abdomen. Infants with prune belly syndrome may develop severe respiratory distress secondary to the thoracic limitation.
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Media type:  X-RAY

Media file 3:  Ultrasound examination of the kidneys shows bilateral hyperechoic kidneys with poor development of the calyces and dilated tortuous ureters.
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Media type:  Photo

Media file 4:  High-detail sonogram of an involved kidney shows a hyperechoic cortex, a dysplastic collecting system, and cortical cysts.
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Media type:  Photo

Media file 5:  In prune belly syndrome, an abdominal sonography usually shows the entire abdomen filled with dilated ureters.
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Media type:  Photo

Media file 6:  On CT, the ureter in this patient with prune belly syndrome fills the entire abdomen.
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Media type:  CT

Media file 7:  Infants with prune belly syndrome show early and marked bilateral vesicoureteral reflux. Significantly more dilatation of the lower ureters exists.
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Media type:  X-RAY

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.
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Media type:  X-RAY

Media file 9:  Typical urethra of prune belly syndrome
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Media type:  X-RAY

Media file 10:  Note the dilated and hypotonic ureters filling the abdomen in an infant with prune belly syndrome.
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Media type:  Photo

Media file 11:
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REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• Ultrasound
• Nuclear Medicine
• Intervention
• Multimedia
• References

• Cromie WJ. Implications of antenatal ultrasound screening in the incidence of major genitourinary malformations. Semin Pediatr Surg. Nov 2001;10(4):204-11. [Medline].
• 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].
• 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].
• 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].
• 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].
• Wakhlu AK, Wakhlu A, Tandon RK, Kureel SN. Congenital megalourethra. J Pediatr Surg. Mar 1996;31(3):441-3. [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].

Article Last Updated: Sep 8, 2005