Rectal bleeding

The passage of blood from the rectum or anus. The blood may be red, dark brown, or black. It may be mixed with, or on the surface of, faeces or passed separately, and there may be pain. Haemorrhoids are the most common cause of rectal bleeding. Small amounts of bright red blood appear on the surface of faeces or on toilet paper. Anal fissure, anal fistula, proctitis, or rectal prolapse may also cause rectal bleeding. Cancer of the colon (see colon, cancer of) or the rectum (see rectum, cancer of), or polyps can also cause bleeding. Disorders of the colon such as diverticular disease may cause dark red faeces. Black faeces ( melaena) may be due to bleeding high in the digestive tract. Bloody diarrhoea may be due to ulcerative colitis, amoebiasis, or shigellosis. Diagnosis may be made from a rectal examination, from proctoscopy, sigmoidoscopy, colonoscopy, or a double-contrast barium X-ray examination.