Defecography: Radiographic examination of the process of defecation after the instillation of a CONTRAST MEDIA into the rectum.Rectal Prolapse: Protrusion of the rectal mucous membrane through the anus. There are various degrees: incomplete with no displacement of the anal sphincter muscle; complete with displacement of the anal sphincter muscle; complete with no displacement of the anal sphincter muscle but with herniation of the bowel; and internal complete with rectosigmoid or upper rectum intussusception into the lower rectum.Rectocele: Herniation of the RECTUM into the VAGINA.Hernia: Protrusion of tissue, structure, or part of an organ through the bone, muscular tissue, or the membrane by which it is normally contained. Hernia may involve tissues such as the ABDOMINAL WALL or the respiratory DIAPHRAGM. Hernias may be internal, external, congenital, or acquired.Defecation: The normal process of elimination of fecal material from the RECTUM.Douglas' Pouch: A sac or recess formed by a fold of the peritoneum.Intussusception: A form of intestinal obstruction caused by the PROLAPSE of a part of the intestine into the adjoining intestinal lumen. There are four types: 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.Pelvic Floor: Soft tissue formed mainly by the pelvic diaphragm, which is composed of the two levator ani and two coccygeus muscles. The pelvic diaphragm lies just below the pelvic aperture (outlet) and separates the pelvic cavity from the PERINEUM. It extends between the PUBIC BONE anteriorly and the COCCYX posteriorly.Constipation: Infrequent or difficult evacuation of FECES. These symptoms are associated with a variety of causes, including low DIETARY FIBER intake, emotional or nervous disturbances, systemic and structural disorders, drug-induced aggravation, and infections.Anal Canal: The terminal segment of the LARGE INTESTINE, beginning from the ampulla of the RECTUM and ending at the anus.Rectum: The distal segment of the LARGE INTESTINE, between the SIGMOID COLON and the ANAL CANAL.Fecal Incontinence: Failure of voluntary control of the anal sphincters, with involuntary passage of feces and flatus.