Lower GI Bleeding



Lesions of the anorectum and colon are by far the commonest causes of lower GI bleeding.
Non-neoplastic Anorectal Lesions. Small amounts of bright red blood on the stool and toilet tissue usually arise from hemorrhoids, anal fis­sures, and fistulae. Proctitis from a variety of in­fectious causes is seen most frequently in male homosexuals and may give rise to hematochezia.

neoplastic Lesions of the Colon and Rectum. Carcinoma of the colon and colonic polyps usu­ally present with chronic blood loss but may pro- i duce brisk bleeding as well.

Ulcerative, Bacterial, and Ischemic Colitis. Bleeding may accompany diarrhea in ulcerative colitis as well as in infectious diarrhea due to En­tamoeba histolytica, Shigella, and Campylobac­ter. In these cases, diarrhea is usually prominent,with mucus and leukocytes in the stool along with constitutional symptoms (e.g., malaise, fever). Is­chemic colitis may cause bloody diarrhea in the elderly.
Colonic Diverticula. The sigmoid colon is the most common site in which large numbers of co­lonic diverticula occur. Those that bleed, how­ever, are most frequently located in the ascending colon and constitute the commonest cause of mas­sive lower GI bleeding. Diverticulitis, in contrast to diverticulosis, is an uncommon source of blood loss.

Angiodysplastic Lesions. Relatively small, ac­quired submucosal arteriovenous malformations called angiodysplastic lesions have become in­creasingly recognized as a common source of bleeding from the cecum and right colon in the elderly. Angiodysplastic lesions may also occur in the upper GI tract and are often difficult to di­agnose either endoscopically or radiographically because they are flat, are located in the submu-cosa, and may be completely obscured by even minor bleeding. These lesions appear to develop with aging and may be responsible for a substan­tial proportion of bleeding previously ascribed to right-sided diverticula. There seems to be an in­creased association of these lesions with calcific aortic stenosis.

Small Intestinal Lesions. Small intestinal le­sions rarely cause GI hemorrhage. Meckel’s div­erticulum is present in the distal ileum of 2 per cent of the population and is the commonest dis­crete lesion of the lower small bowel to bleed acutely.