Vitelline cyst in the rat ileum

Congenital vitelline ductanomalies other than Meckel’s diverticulumare rare in animals. A cystof approximately 8 mm in diameter was observed on the antimesenteric surface of the ileal serosa in a 10-week-old female Crl:CD(SD) rat. Microscopically, the cystclosely resembled the ileum, but it did not communicate with the ileal lumen. We diagnosed this case as a vitelline cystderived from the vitelline ductbased on the location where it developed and its histological behavior. In rats, only Meckel’s diverticulumhas been reported with a congenital anomaly of the vitelline duct, and no other spontaneous anomalies including a vitelline cysthave been reported. This case may be the first report concerning a vitelline cystin the rat ileum.