Causes of Heavy Bleeding from the Large Intestine

Large amounts of maroon blood from the rectum is called hematochezia. This type of gastrointestinal (GI) bleeding most commonly originates from the lower GI tract. Bleeding from the upper GI tract can present as hematemesis (vomiting blood) and/or melena (dark "old" blood from rectum). Upper GI bleeding is the cause of hematochezia in only a minority of cases, and usually involves massive bleeding.

There are many causes of significant lower GI bleeds. Hemorrhoids are a frequent cause of lower gastrointestinal bleeding. However, hemorrhoidal bleeding is generally minor, only coating stool with blood or spotting toilet paper.

Bleeding from colorectal cancer:

Colorectal cancer is responsible for approximately 10 percent of cases of rectal bleeding in patients over age 50. The most common presentation of colorectal cancer is hematochezia or melena, change in bowel habits, and/or abdominal pain. Other possible signs and symptoms of colorectal cancer include abdominal distention, nausea, vomiting, weight loss, fatigue, anemia and weakness. Additionally, bleeding from cancers of the colon or rectum tends to be low grade and recurrent, as it is the result of overlying erosion or ulceration of the intestine.

Colonoscopy is the best diagnostic test for colon cancer and rectal cancer in symptomatic individuals, since it can localize lesions throughout the large bowel. Hematochezia is more often a sign of rectal cancer rather than colon cancer, while a change in bowel habits is a more common presenting symptom for left-sided colon cancers (which tend to be encircling, constricting lesions).

Bleeding from IBD:

Ulcerative and inflammatory diseases of the colon are common causes of lower gastrointestinal bleeding. The inflammatory bowel disorders Ulcerative colitis and Crohn's disease are associated with many other symptoms such as diarrhea, abdominal pain and extraintestinal skin, joint and eye symptoms. Ulcerative colitis and Crohn's disease are diagnosed using endoscopic imaging and biopsy in conjunction with confirmatory lab tests.

Bleeding from diverticula:

Diverticular bleeding is the most common cause of brisk hematochezia, accounting for over 30 percent of cases of massive rectal bleeding. Many patients with diverticular bleeding, which occurs in 15 percent of patients with diverticulosis, are elderly. Diverticular bleeding occurs when a vessel in the dome of the herniating diverticulum is exposed to recurrent injury over time. This leads to weakness and eventual rupture of the vessel wall. Constipation requiring straining during bowel movements can contribute to vessel weakening and lead to a diverticular bleed. This non-inflammatory cause of lower GI bleeding results in no symptoms associated with the bleeding, other than bloating discomfort in some patients.

Diverticular bleeding is detected on colonoscopy as active bleeding from a diverticulum, a nonbleeding visible vessel, or an adherent clot. The most common source of bleeding diverticula is in the right colon. Bleeding often stops spontaneously in the majority of patients who require blood transfusion of less than four units of blood per day.

Bleeding from angiodysplasia:

Angiodysplasia, a small malformation of blood vessels in the gut, is a possible cause of lower GI bleeding. This condition has a very similar presentation to diverticular bleeding. Angiodysplasia often presents as painless hematochezia that is episodic and self-limiting in nature. It is also the most common source of hematochezia in patients over age 65.

Coagulopathies (bleeding disorders) are associated with bleeding from angiodysplasias. Certain medications such as warfarin or high dose aspirin may increase the likelihood of bleeding due to angiodysplasia. On endoscopy, angiodysplasia appears as peripherally expanding dilated capillaries.