blood in stool

Blood in stool can be a sign of a life threatening disease like cancer or a vexing but benign condition like hemorrhoid. Blood in the stool can be visible or invisible. When it is visible, it can be black and tarry (melena), burgundy (maroon) or bright red. When it is invisible, it can only be detected by a stool test. Stool-based tests for colon cancer are designed to detect blood in the stool.

Why do I have blood in stool?


Hemorrhoids are swollen veins around the anus or lower part of the rectum. They are common affecting more than 50% of people over the age of 50. Sometimes they bother people and sometimes they don’t. They may cause painless rectal bleeding or what is called “bright red blood per rectum.” They can be inside or outside. They do not lead to cancer. For more information on hemorrhoids, click HERE.


Colitis is inflammation of the colon. This can be acute or chronic. Colitis can be due to infection, ischemia, or inflammatory. Infection or ischemia (when blood supply is blocked) can lead to acute colitis. Chronic inflammation is usually due to inflammatory bowel disease. There are 2 types of inflammatory bowel disease-ulcerative colitis and crohn’s disease.

Diverticular disease

The presence of a diverticulum or diverticula in the colon is called diverticulosis. A diverticulum is a pouch within the wall of the colon. Inflammation of the pouch is called diverticulitis. Diverticula can bleed without inflammation or infection. Diverticulitis can also lead to blood in the stool.


Angiodysplasia is also called angioectasia or arteriovenous malformation (AVM). These are abnormal blood vessels on the wall of the colon. They can also be present in any part of the gastrointestinal tract. They may bleed on and off.

Solitary rectal ulcer syndrome 

This is a rare condition that is associated with constipation. Solitary rectal ulcer syndrome causes rectal bleeding, straining during defecation and a sense of incomplete evacuation.

Colorectal cancer 

By far the most worrisome reason why you may have blood in the stool is colorectal cancer. It is a leading cause of cancer deaths in the U.S. If you have blood in the stool and have not recently had a colonoscopy, you probably need one. If your stool test is positive for blood, you need a colonoscopy. Read Colorectal Cancer in 2018: The Good, the Bad and the Ugly.


There are many other reasons why you may have blood in the stool. The blood may be coming from your upper gastrointestinal tract (esophagus, stomach and small intestine). An ulcer or cancer in the esophagus, stomach or small intestine can also make you have blood in the stool. Blood in stool may be due to a bleeding or clotting disorder. Also, certain medications like blood thinners may make bleeding worse.

You should see a physician if you have blood in your stool.


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