Early Fetal Bladder Shunt May Soften Prune Belly Syndrome, Case Report Suggests

A single case report published in Frontiers in Urology has reignited one of the longest-running debates in pediatric urology: what actually causes prune belly syndrome, and could intervening in the womb change how the disease expresses itself? The case, described by a team from Reina Sofia University Hospital in Córdoba and Hospital Universitario Clínico San Cecilio in Granada, Spain, follows a male fetus diagnosed at just 12 weeks of gestation with a severely enlarged bladder and massive dilation of both upper urinary tracts. After surgeons placed a vesicoamniotic shunt at 16 weeks to drain the bladder into the amniotic cavity, the fetus developed only a mild, incomplete form of the syndrome after birth, a finding the authors say is consistent with the idea that prolonged fetal bladder distension actively drives the disorder’s most damaging features.

Prune belly syndrome, also known as Eagle-Barrett syndrome, is a rare congenital disorder classically defined by a triad of findings: deficiency of the abdominal wall musculature, dilation of the urinary tract, and bilateral cryptorchidism, meaning both testes fail to descend into the scrotum. Its estimated incidence ranges from 1 in 30,000 to 50,000 live births, and more than 95 percent of affected patients are male. Incomplete phenotypes, commonly referred to as pseudo-prune belly syndrome, account for roughly 3 to 5 percent of cases and exhibit variable combinations of the classical features. The wrinkled, prune-like appearance of the abdomen that gives the syndrome its name results from the absence or underdevelopment of the abdominal muscles, which leaves the overlying skin loose and redundant.

The pathogenesis of the syndrome has remained controversial for decades. Two main hypotheses have been proposed. The first, a primary mesodermal developmental defect, holds that a single embryological abnormality affects the abdominal wall, the urinary tract, and the genital structures simultaneously from the earliest stages of development. The second, the fetal outlet obstruction hypothesis, attributes the syndrome to prolonged bladder distension during fetal life, which stretches and thins the developing abdominal wall, causes progressive urinary tract dilation, and impairs normal testicular descent. More recently, pathogenic variants in genes such as CHRM3, FLNA, and HNF1B have suggested a developmental contribution in some patients, leading most experts to view the condition as multifactorial, arising from an interaction of developmental, obstructive, and genetic factors.

In the reported case, a pregnant woman was referred to the fetal medicine unit after routine prenatal ultrasonography revealed severe bilateral hydroureteronephrosis associated with marked fetal megacystis, measuring 20 by 22 millimeters, at 12 weeks of gestation. At that point, the amniotic fluid volume was within normal limits. By 15 weeks, the bladder had enlarged dramatically to 40 by 43 millimeters and displayed the characteristic keyhole sign, a configuration suggesting obstruction at the bladder outlet. The case was discussed at a multidisciplinary prenatal meeting, where fetal bladder decompression was considered because of the significant bladder enlargement and the potential risk of compressive complications to the developing kidneys and lungs.

The patient was referred to a tertiary fetal therapy center, where a Somatex intrauterine shunt was placed at 16 weeks of gestation. Vesicoamniotic shunting is the most widely used fetal decompression technique, aiming to preserve renal development, maintain amniotic fluid volume, and reduce pulmonary morbidity. Subsequent weekly ultrasound examinations demonstrated complete resolution of the bilateral hydroureteronephrosis, persistent decompression of the bladder, and appropriate shunt positioning throughout pregnancy. Gestation progressed uneventfully except for worsening of the mother’s diabetes mellitus, and delivery was induced at 36 weeks because of complications related to that condition.

The newborn did not exhibit respiratory distress and required no ventilatory support, an encouraging sign given that pulmonary hypoplasia is one of the main determinants of prognosis in severe lower urinary tract obstruction. Urethral catheterization was attempted shortly after birth, but passage of the catheter proved difficult and was ultimately achieved under ultrasound guidance using a hydrophilic guidewire. After confirmation of appropriate bladder drainage, the vesicoamniotic shunt was removed without complications. Physical examination revealed bilateral cryptorchidism, with a non-palpable right testis and a left testis palpable within the inguinal canal, along with mild abdominal wall laxity that became progressively more evident during the neonatal period.

Postnatal imaging told a striking story. Renal and urinary tract ultrasonography performed at 48 hours and again at 7 days of life demonstrated complete resolution of the prenatal hydroureteronephrosis, with normal renal morphology and no evidence of upper urinary tract dilation. Serum renal function parameters were within normal limits, and a dimercaptosuccinic acid renal scan showed preserved bilateral cortical function without scarring. Voiding cystourethrography, however, revealed a markedly enlarged bladder associated with bilateral high-grade vesicoureteral reflux of grades IV to V and mild urethral dilation. Diagnostic cystoscopy was then performed to clarify the underlying anatomy.

The endoscopic evaluation excluded posterior urethral valves and urethral atresia, two of the most common congenital causes of fetal bladder outlet obstruction, and instead demonstrated mild narrowing of the prostatic urethra, a large-capacity bladder, and orthotopic ureteral orifices with a refluxing appearance. The differential diagnosis of fetal megacystis also includes megacystis-microcolon-intestinal hypoperistalsis syndrome and cloacal malformations, but the absence of associated gastrointestinal or cloacal abnormalities made those conditions unlikely. Taken together with the prenatal imaging findings and the postnatal phenotype, the clinical picture favored an attenuated presentation consistent with pseudo-prune belly syndrome rather than another congenital cause of fetal lower urinary tract obstruction.

The clinical evolution during the first six months of life was favorable by nearly every measure. The urethral catheter was removed at 15 days of life, after which spontaneous voiding was normal. At 3 months of age, spontaneous descent of the right testis into the inguinal canal and of the left testis into the scrotum was observed, and by the 6-month follow-up, bilateral testicular descent had completed without surgical intervention. The patient remains asymptomatic, has experienced no urinary tract infections while on continuous low-dose antibiotic prophylaxis, and the abdominal wall weakness has remained stable without progression. Renal ultrasound demonstrates appropriate bilateral renal growth without hydronephrosis, and renal function remains within normal limits.

The authors are careful to acknowledge the limits of what a single observation can prove. Genetic testing was not performed in this patient, and the absence of molecular evaluation means an underlying genetic contribution to the phenotype cannot be excluded. The terminology surrounding incomplete presentations also remains contested, with some authors classifying similar cases as incomplete prune belly syndrome rather than pseudo-prune belly syndrome, and the authors note that the label should be interpreted within the context of the disease’s heterogeneous spectrum. Nevertheless, they argue that the diagnosis of pseudo-prune belly syndrome was more appropriate in this patient because, despite the presence of abdominal wall hypoplasia and bilateral cryptorchidism, the severe urinary tract abnormalities resolved almost completely following early prenatal decompression, meaning the classic triad was never fully expressed after birth.

The mechanistic implications are what make the case remarkable. According to the mechanical theory, prolonged fetal bladder distension leads to progressive stretching and thinning of the developing abdominal wall musculature, and the resulting reduction in intra-abdominal pressure may subsequently impair normal testicular descent. In this case, despite severe fetal megacystis during early gestation, prompt decompression through vesicoamniotic shunting resulted in the preservation of renal morphology and function, spontaneous partial testicular descent during infancy, and the development of only a mild phenotype rather than complete prune belly syndrome. These findings could suggest that bladder overdistension plays an active pathogenic role in the development of abdominal wall deficiency and cryptorchidism, rather than representing a secondary consequence of an underlying developmental abnormality.

Conversely, if the syndrome were exclusively caused by a primary mesodermal defect affecting the abdominal wall, urinary tract, and gonadal structures from the outset, one would expect prenatal urinary diversion to have little or no influence on the final phenotype. Under such circumstances, decompression of the urinary tract would be unlikely to alter the developmental trajectory of the syndrome. Although a single case cannot refute the mesodermal hypothesis, the favorable evolution observed here raises the possibility that mechanical factors contribute substantially to disease severity and that timely fetal decompression may attenuate the progression toward the complete phenotype. The authors also point out that experimental work in fetal lambs has previously shown that early bladder outlet obstruction can induce renal dysplasia and prune belly-like features, lending additional weight to the obstructive model.

For now, the authors emphasize that causality cannot be inferred from a single clinical observation and that larger prospective studies are required before definitive conclusions regarding treatment effect can be drawn. Longer-term follow-up will also be needed to assess bladder function, continence, renal function, and overall functional outcomes as the child grows. Yet the case stands as a provocative data point in a field where evidence is scarce and phenotypes are highly variable. If early fetal decompression can indeed modify phenotypic expression in selected patients, the implications extend beyond surgical technique to the fundamental question of how the prune belly spectrum takes shape, and whether the window for intervention opens earlier than anyone had previously thought.

Subject of Research: Science news article on a case report suggesting early fetal bladder decompression may attenuate prune belly syndrome phenotype

Article Title: Case Report: Pseudo-prune belly syndrome after early fetal bladder decompression: implications for the pathogenesis of prune belly spectrum disorders

Article References: Parente, A., Fariñas, M., Miño, M., & Molina, F. S. (2026). Case Report: Pseudo-prune belly syndrome after early fetal bladder decompression: implications for the pathogenesis of prune belly spectrum disorders. Frontiers in Urology, 6, Article 1919700. https://doi.org/10.3389/fruro.2026.1919700

Image Credits: AI Generated

DOI: 10.3389/fruro.2026.1919700

Keywords: prune belly syndrome, pseudo-prune belly syndrome, vesicoamniotic shunting, fetal surgery, lower urinary tract obstruction, megacystis, cryptorchidism, prenatal diagnosis, Eagle-Barrett syndrome, fetal outlet obstruction hypothesis, pediatric urology, hydroureteronephrosis