Sometimes the mesenteries of the ascending and descending colon fail to undergo normal fixation. In such case, the small intestines (jejunum and ileum) hang by a narrow stalk that contains the superior mesenteric vessels. The intestines twist around this stalk producing a mid-gut volvulus. The superior mesenteric vessels are compressed and blood supply to the twisted segment of the gut is often restricted; complete obstruction of the circulation leads to infarction and gangrene.