Prune Belly Syndrome Differential Diagnoses

Updated: Sep 25, 2023
  • Author: Israel Franco, MD, FAAP, FACS; Chief Editor: Bradley Fields Schwartz, DO, FACS  more...
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Diagnostic Considerations

Pseudo–prune belly syndrome

Pseudo–prune belly syndrome, which is associated with prune belly syndrome uropathy, is characterized by normal abdominal wall examination findings and incomplete or absent cryptorchidism. In a study of 8 patients with this syndrome, 5 (63%) eventually developed kidney failure. [18]

Prune belly–like variant

An abdominal wall defect commonly confused with prune belly syndrome has been termed prune belly–like variant. Some studies have reported abdominal wall defects without urologic anomalies. This defect involves only the abdominal wall muscles, in particular the internal and external obliques, as well as the transversalis muscles. In contrast with prune belly syndrome, the rectus muscles are not involved.

This defect causes weakness laterally, with bulging of the abdominal wall just below the rib cage. In such cases, CT scans of the abdominal wall reveal preservation of the rectus and obliques away from the area. The authors have surgically reconstructed two such defects in young male patients using a laparoscopic modification of the Firlit procedure, with excellent results. This syndrome may be associated with in utero distention of the abdominal cavity.

The patient pictured below had evidence of in utero megalocystis that resolved spontaneously.

The lateral subcostal weakness in this patient is The lateral subcostal weakness in this patient is due to absence of the internal and external obliques subcostally.
Bilateral subcostal incisions exposed the fascial Bilateral subcostal incisions exposed the fascial defects.
Note that the previously attenuated fascial defect Note that the previously attenuated fascial defect has been covered by reapproximated muscle.
Laparoscopic view of the fascial defect transillum Laparoscopic view of the fascial defect transilluminated from outside the abdomen. Note that the defect is just a thin layer of attenuated fascia.

Lower urinary tract obstruction

On prenatal ultrasound, fetuses with prune belly syndrome have many sonogram findings comparable to those with lower urinary tract obstruction (LUTO) from causes including posterior urethral valves, ureterocele, and urethral atresia, as well as mimics such as megacystis-microcolon-intestinal-hypoperistalsis syndrome (MMIHS). [2]

Classic findings of LUTO in male fetuses include the following [19] :

  • Bilateral hydroureteronephrosis
  • Megacystis
  • Keyhole sign (dilation of the proximal urethra and an associated thick-walled distended bladder, due to posterior urethral valves) [20]
  • Bladder wall thickening
  • Oligohydramnios

However, not all fetuses with LUTO have that classic constellation of ultrasound findings. For that reason, Rickard et al developed and validated the Toronto nomogram, a prenatal ultrasound index to predict LUTO and prune belly syndrome. In their study of 84 male fetuses with moderate to severe hydronephrosis on ultrasound, the nomogram demonstrated 84.2% sensitivity and 95.4% specificity, with three false positives. [19]