Retroarterial colon with right-sided obstructive gangrenous colitis

Retroarterial colon is a rare entity in which the colon is located behind the superior mesenteric vessels. Transmesenteric internal hernias result in portions of the bowel protruding through a defect in the mesentery and are often acquired but may be congenital. We report a 10-year-old female with trisomy 13 who lacked retroperitoneal fixation of the intestines and had a retroarterial transverse colon possibly resulting from a congenital transmesenteric internal hernia, that eventually lead to obstructive gangrenous colitis.