Congenital Positional Anomaly of Descending Colon and Sigmoid Colon: Its Embryological Basis and Clinical Implications

The rotation of the midgut is essential for normal placement of intestines in the abdominal cavity. The process of midgut rotation and simultaneous retraction of the herniated intestinal loops pushes the hind gut to the left side of the abdominal cavity. So the descending colon and the sigmoid colon occupy the left side of the abdominal cavity. In this report, we document a male cadaver that revealed right-sided sigmoid colon. On further dissection, the descending colon was found lying in the midline with a small peritoneal fold stretching from the right side of sigmoid colon to ileocecal junction. There was also variation in the inferior mesenteric artery supplying the displaced descending colon and sigmoid colon. The possible embryological and molecular basis of this variation has been discussed. The anatomical knowledge of this variation is essential for interventional and diagnostic colonoscopy procedures and colonic surgeries.