Reviewed by: HU Medical Review Board | Last Reviewed: January 2018.
- Jet black stool (also called melena).
- Bright red blood mixed with stool (also called hematochezia).
- Blood on the toilet paper or in the toilet, without stool.
What causes black stool?
Bleeding higher up in the digestive tract (esophagus, stomach) usually causes black stool. One of the main forms of IBD, Crohn’s disease, can be a possible—but uncommon—cause of black stool.3 It can be hard to notice this type of bleeding. Special stool tests may be needed to identify blood in dark stool.
Is it more common in Crohn's or ulcerative colitis?
Rectal bleeding is more common in ulcerative colitis. Bleeding in the lower digestive tract (last part of small intestine, colon, rectum, or anus) causes bright red blood to appear. This is a more common symptom of Crohn’s disease, which typically affects the end of the small intestine (ileum) and colon, and ulcerative colitis, the other main form of IBD which affects the colon.4
Among people with IBD, rectal bleeding is more typical of ulcerative colitis than Crohn’s disease.1 Bleeding related to inflammation in the colon often occurs along with diarrhea.5Anal fissures and fistulas can cause bright red blood in the stool.2,4
Severe rectal bleeding (hemorrhage) can cause low blood pressure, increased heart rate, and shock.4 Hemorrhage leads to hospitalization in 1.2% of patients with Crohn’s disease and 0.1% of ulcerative colitis.4
What causes rectal bleeding?
In general, hemorrhoids and diverticular disease are the most common causes of rectal bleeding.2,5 Other common causes include:
- Angiodysplasia of the colon (fragile blood vessels)
- Colon inflammation (colitis) from many causes
- Stomach ulcers
- Colorectal cancer
Bleeding in the lower digestive tract has been linked to taking non-steroidal anti-inflammatory drugs (NSAIDs), such as Aleve, Advil, and Motrin.4 Once you have been diagnosed with IBD, NSAIDs are not recommended.6
However, research about the link between NSAIDs and IBD is ongoing and so far, inconclusive. No studies have shown that taking these medications is a cause of IBD.7
How is it evaluated and diagnosed?
Your health care provider will evaluate rectal bleeding by asking questions, performing a physical exam, and doing some tests.
Your provider may ask questions such as:3,4,8
- What are your bowel movements like?
- Have you had any recent changes in bowel habits?
- Are your stools black or bloody? How often does this happen?
- Have you noticed blood on the toilet paper?
- Have you vomited recently? What did it look like?
- Have you had a recent colonoscopy?
- Have you had any recent trauma to the abdomen or rectum?
- What medications are you taking?
- Do you have a history of digestive or blood diseases?
- Have you been treated for prostate or pelvic cancer?
- Has anyone in your family had colon cancer?
- Have you experienced changes in weight recently?
Your health care provider may want to look at your stool.4 If you are in the hospital, you may be asked to use a special toilet or bedpan. If you are at home, your provider will instruct you on how to collect a sample.
What tests are done to find causes of blood in stool?
Your provider will check your pulse and blood pressure. He or she will probably also perform a rectal examination to look for hemorrhoids, fistulas, or fissures that could cause bleeding. You may need to have blood tests to check for anemia, clotting problems, and changes in your blood chemistry.
Your health care provider may recommend a colonoscopy.2 This procedure allows your provider to see inside your digestive tract and look for the source of bleeding. Colonoscopy is helpful for people with unexplained bleeding and bleeding that continues despite treatment. Colonoscopy is especially important if you have lost weight, are anemic, are older than 40, or have a family history of colorectal cancer.
What is the treatment for rectal bleeding from Crohn's or UC?
Similarly, bleeding due to complications from IBD is managed by treating the complication. For fissures, the first step is trying to let it heal on its own. If the fissure does not heal, medications and surgery are used. Anal fistulas also are treated with a combination of medication and surgery.