Solitary rectal ulcer syndrome. Endoscope image of an ulcer in the rectum, the terminal portion of the large intestine. This is a rare syndrome, whose cause is not known. It often occurs in those with chronic constipation, in which cases it may be caused by excessive straining during a bowel movement. Symptoms include rectal pain and bleeding. Treatments include topical drugs, stool softeners and increasing fibre and fluid in the diet. The condition is often recurrent and can lead to rectal prolapse.