Most cases of rectal bleeding are minor and resolve on their own. Dark, tarry stools typically stem from bleeding in the upper gastrointestinal tract, such as the stomach or esophagus. Bleeding from the large intestine or rectum is more often bright red, indicating fresh, undigested blood. But heavy rectal bleeding, or that associated with dizziness or faintness, can be a medical emergency.
Hemorrhoids
Hemorrhoids are the most common cause of minor rectal bleeding, according to the American Society for Gastrointestinal Endoscopy. A hemorrhoid is an engorged vein in the rectum or anus. They usually arise from an increase in pressure in the area that results from straining with constipation or heavy lifting. They are most often painless, but a lump might be felt. Bleeding from hemorrhoids is usually discovered after a bowel movement.
Fissures
An anal fissure is a small rent in the tissue of the anus. They can be quite uncomfortable, but are rarely serious. The bleeding is often noted after the painful passage of hard stool. Fissures can also develop in those who have an inflammatory condition of the rectum.
Colitis
Colitis is inflammation of the colon. More specifically, proctitis is an inflammation of the rectum. This may be the result of an infection, after radiation therapy or from an inflammatory bowel disease such as Crohn's disease or ulcerative colitis. Any of these conditions may cause bleeding from the rectum, notes the National Digestive Diseases Information Clearinghouse.
Diverticulosis
Diverticulosis is a common cause of rectal bleeding, according to Emedicine.com. Diverticuli are small pouches that form in the large intestine. These pockets tend to be near blood vessels and the tissue over them thins, making them prone to bleeding. Diverticulitis is the result of infection or inflammation in one of the pouches, but does not necessarily increase the chance of bleeding.
Angiodysplasia
Angiodysplasia is characterized by a malformation of blood vessels. In this case, those vessels are in the lower gastrointestinal tract. Angiodysplasia is thought to be the result of degeneration of the walls of arteries and veins, which develop as people age, according to Emedicine.com.
Polyps and Cancer
A polyp is a benign growth of tissue into the space of the intestine. They sometimes turn into cancer. Either polyps or cancerous tumors can bleed. The National Digestive Diseases Information Clearinghouse lists cancer as a common cause of microscopic bleeding from the rectum.
