ABSTRACT
Colorectal cancer is a common condition. It remains the third most common cancer in the UK currently with 32,000 new cases and 17,000 deaths per annum. Rectal carcinoma accounts for 37% of all large-bowel cancers; 75% of colorectal cancers are in either the rectum or distal colon; 25% are found proximal to the splenic flexure; 4–5% of patients have synchronous lesions. Fresh blood per rectum, i.e. bright red as opposed to altered blood, is usually distal colonic or rectal in origin. Bleeding from the proximal colon may be darker. This must be distinguished from melaena, which is black, tarry stool, and originates from the upper GI tract. Melaena is partially digested blood, and may or may not co-exist with haematemesis. Rapid upper GI haemorrhage may cause fresh rectal bleeding rather than melaena, due to irritation of the bowel and consequent rapid transit through the intestine.
