What is Invaginations, Intestinal?

The prolapse of one part of the intestine into the lumen of an immediately adjoining part. There are four varieties: colic, involving segments of the large intestine; enteric, involving only the small intestine; ileocecal, in which the ileocecal valve prolapses into the cecum, drawing the ileum along with it; and ileocolic, in which the ileum prolapses through the ileocecal valve into the colon. (Dorland, 27th ed)