You are in: eMedicine Specialties > Radiology > PEDIATRICS Prune Belly SyndromeArticle Last Updated: Jul 3, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Beverly P Wood, MD, MS, PhD, Professor, Departments of Radiology and Pediatrics, Division of Medical Education, Keck School of Medicine, University of Southern California Beverly P Wood 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 Editors: Robert J Starshak, MD, Medical Director, Assistant Clinical Professor, Department of Radiology, Medical College of Wisconsin, Falls Medical Group; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; John Karani, MBBS, FRCR, Consulting Staff, Department of Radiology, King's College Hospital, London Author and Editor Disclosure Synonyms and related keywords: prune belly syndrome, congenital absence of abdominal musculature, deficiency of abdominal musculature, Eagle-Barrett syndrome, triad syndrome INTRODUCTIONSection 2 of 10
  BackgroundPrune 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 PathophysiologyThe 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.4, 5 FrequencyUnited StatesPrune belly syndrome is a rare anomaly seen in 1 in 35,000-50,000 live births. The genetic origins remain unclear. Mortality/MorbidityControversy 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. RacePrune belly syndrome occurs in individuals of all races. SexPrune 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. AgeThe 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. AnatomyAbdominal 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. 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. Clinical DetailsSee Anatomy. Preferred ExaminationTo 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 (99mTc) dimethylsuccinic acid (DMSA) renal scan. DMSA is a cortical agent; DMSA renal scans provide information about both the appearance and function of the kidneys. DIFFERENTIALSSection 3 of 10
Posterior Urethral Valve Pulmonary Hypoplasia Other Problems To Be ConsideredMegacystis microcolon
RADIOGRAPHSection 4 of 10
FindingsRadiographic findings in prune belly syndrome are as follows:
For those who have access to nuclear radiology, a scan using a cortical agent such as 99mTc DMSA is useful 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) may be helpful in visualizing the kidneys and collecting systems. Degree of ConfidenceThe radiographic appearance is virtually always characteristic of prune belly syndrome. CT SCANSection 5 of 10
FindingsFindings 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 6). ULTRASOUNDSection 6 of 10
FindingsSonography 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 alone6, 7, 8 (see Images 3-5, Image 10). Degree of ConfidenceOn 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/NegativesMegacystis-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 MEDICINESection 7 of 10
FindingsRenal 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. INTERVENTIONSection 8 of 10
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.9, 10, 11, 12 MULTIMEDIASection 9 of 10
REFERENCESSection 10 of 10
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