Rectal prolapse normally describes a medical condition wherein the walls of the rectum protrude through the anus and hence become visible outside the body.
Prolapses may involve the full thickness of the rectal wall, or the rectal mucosa only (mucosal prolapse). They may be external if they protrude from the anus and are visible externally, or internal if they do not protrude externally. The term intussusception refers to invagination, or infolding. When the term "intussusception" is used by itself, this usually refers to a condition where one segment of the intestine (or bowel) folds within another. This can be a medical emergency, in contrast with rectal intussusception which is not life threatening. Rectal intussusception therefore refers to the prolapsed section of bowel folding back on itself.