Omphalocele with Patent Omphalomesenteric Duct and Intestinal Prolapse in a Preterm Neonate: Histopathological Evidence of Incomplete Vitelline Duct Involution.

Patent omphalomesenteric duct (OMD) with intestinal prolapse coexisting with omphalocele is an exceptional ventral folding anomaly that may be misdiagnosed as gastroschisis. The vitellointestinal duct normally involutes between the seventh and ninth gestational weeks; failure of obliteration produces a spectrum of anomalies including Meckel diverticulum, fibrous bands, umbilico-ileal fistulae, or, rarely, a fully patent duct with bowel prolapse. Fewer than 15 cases of the combined anomaly have been reported since 1967. We describe a preterm neonate (32 + 4 weeks, 2160 g) with an intact omphalocele sac and a separate, widely patent OMD through which both the proximal and distal limbs of the terminal ileum had prolapsed. Histopathological examination of the resected sac and OMD-bearing ileal segment demonstrated the umbilical cutaneous transition with vitelline-derived vascular remnants, preserved intestinal architecture with intact myenteric ganglion cells, and no heterotopic gastric or pancreatic mucosa. These findings indicate persistence of a fully patent vitellointestinal duct at the morphologically simple end of the vitelline duct anomaly spectrum, supporting a developmental rather than an acquired origin. The case illustrates the diagnostic pitfall of misidentification as gastroschisis and the value of clinicopathological correlation in establishing the developmental basis of this rare anomaly.