The tendency for rectal prolapse is genetic. I have some data from years back that in sheep this tendency passes along the male line and on the sex linked gene. The tissue that attaches the rectum to the pelvic cavity is weakened and some factor (coughing, etc)causes the tissue to rupture and a proplase occurs. It can be repaired at least in sheep by sutures and deep injections of an irritant at 3 points around the anus. This causes scar tissue to form anchoring the rectum to the pelvic cavity.