Uncommon and Common Causes of GI Bleeding

By Barbara Bolen, PhD 

 Medically reviewed by Jay N. Yepuri, MD

It can be distressing to find blood in your stool, the causes of which range from relatively minor conditions like hemorrhoids to severe ones like colon cancer. In some cases, red stools may not even be caused by bleeding but by certain foods or medications that you've eaten.

No matter the cause, it's important to see a healthcare provider if you find evidence of blood in your stools.

This article looks at some of the common and uncommon causes of blood in stool and conditions that are sometimes mistaken for a bleed in the digestive tract. It also describes the various signs and symptoms that warrant an immediate medical investigation or emergency care.

Common Causes of Blood in Stool

The two things healthcare providers typically consider when there is blood in stool are hemorrhoids and anal fissures. This is especially true if you are passing bright red blood, a condition called hematochezia. This often means there is a bleed in the lower digestive tract.

Dark red or brownish-red blood generally suggests that the bleeding is higher up in the gastrointestinal (GI) tract. Black or tarry stool could also indicate an upper GI bleed.1

Hemorrhoids and anal fissures involve bleeding in or near the anus that can collect on stools during a bowel movement.

Verywell / JR Bee

Hemorrhoids

Hemorrhoids occur when blood vessels in the rectum or anus become swollen and inflamed. They are common, especially during pregnancy. Bleeding from hemorrhoids can develop if you are constipated, and hardened stools scrape vulnerable tissues. It can also be the result of straining, which increases pressure within the swollen blood vessel.2

In addition to bright red blood in stools, symptoms of hemorrhoids include:2

• Anal itching

• A hard, tender lump near the anus

• Anal pain or ache, especially when you sit

• Rectal bleeding, often noticed when wiping with toilet paper

You can usually treat hemorrhoids at home by:3

• Eating a high-fiber diet or using fiber supplements

• Taking a stool softener

• Drinking more water

• Avoiding straining when passing stool

• Taking a sitz bath several times a day

• Using an OTC hemorrhoid cream, suppository, or ointment

Anal Fissures

An anal fissure is a tear in the lining of your anus. Common causes include passing large stools, chronic diarrhea, straining, pregnancy, childbirth, and anal sex.

In addition to bright red blood in stools, symptoms of anal fissure may include:4

• Anal pain or itching

• Pain during and after bowel movements

• A visible cut or tear in the skin around your anus

• Rectal bleeding

You can often treat minor anal fissures at home by:4

• Increasing fiber intake

• Drinking more water

• Taking stool softeners

If home treatments don't improve a mild anal fissure within five to six weeks, contact your healthcare provider. Do not wait if the pain or bleeding is severe.5

Less Common Causes of Blood in Stool

Less frequent causes of GI bleeding involve a bleed higher up in the digestive tract. This is recognized by blood in the stool that is usually more maroon, brown, or blackish.

The color change results from the rapid oxidation of an iron-rich substance in the blood (called hemoglobin) as stools pass through the digestive tract. The higher the bleeding, the more extensive the oxidation and the darker the color. Some stools can even end up looking black and tarry, a condition known as melena.

There are five conditions for which this type of GI bleed might occur.

Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) comes in two forms: ulcerative colitis and Crohn's disease. Both cause persistent inflammation in the large and small intestines.6

Blood in the stool is a characteristic symptom of ulcerative colitis, though it is less common in Crohn's disease. That said, the color of blood can vary based on where in the digestive tract the bleeding is occurring.6

In addition to blood in stool, other symptoms may include:6

• Persistent, urgent diarrhea

• Abdominal pain and cramping

• Fever

• Constipation

• Loss of appetite

• Unintended weight loss

• Fatigue

Ulcerative colitis and Crohn's disease are typically treated with diet and medications called aminosalicylates, corticosteroids, immunosuppressants, and biologics that temper the underlying inflammation in different ways. In severe cases, surgery is needed.7

Diverticular Bleeding

Diverticular disease occurs when small pouches (called diverticula) develop in the lining of your large intestine. Most people with this condition have no symptoms. However, some people can develop diverticulitis, which is caused by infection or inflammation of one of the pouches. Although not terribly common, these pouches can sometimes bleed. If this happens, you may see a large amount of blood in your stool.8

HealthLinkBC. Diverticular bleeding.

In addition to blood in stools, symptoms of diverticulitis may include:9

• Abdominal pain, which can be severe

• Bloating

• Fever or chills

• Nausea and vomiting

• Loss of appetite

Treatment depends on the complications of diverticular disease. In general, a high-fiber diet and increased water intake are recommended. Antibiotics are used to treat diverticulitis. Severe cases of diverticulitis or recurrent diverticular bleeding may require surgery (colectomy) to remove part of the colon.10

When to Call 911

Diverticular bleeding will usually stop suddenly. However, in a small number of cases, the bleeding can become life-threatening and require emergency care. If ever you have profuse rectal bleeding and large amounts of blood on your stool, call 911 or go to your nearest emergency room.10

Upper Digestive Tract Bleeding

Digestive disease occurring higher up in the digestive tract (including the esophagus, stomach, and small intestine) can also cause blood in stools. Examples include peptic ulcers, esophagitis, esophageal tears, and tumors.11

If you have upper digestive tract bleeding, you will typically experience black, tarry stools (referred to as melena).11

Other symptoms of upper digestive tract bleeding include:11

• Bloody vomit

• Vomit with a coffee ground appearance (due to the formation of blood clots)

• Abdominal cramps

• Dizziness

• Shortness of breath

• Fatigue and weakness

• Pallor (looking pale)

The treatment of severe upper digestive tract bleeding varies depending on the cause, but it can include epinephrine (adrenaline) injections to rapidly shrink bleeding blood vessels and cauterization (burning) of blood vessels with electricity or heat to stop the bleeding. Clips or bands may also be placed around vessels to cut off the blood flow.12

Colon Cancer

Blood in the stool is often the first noticeable sign of colon cancer.13 This is why it is essential that any signs of blood in your stool be brought to the attention of your healthcare provider.

With colon cancer, the color of the bloody stool can range from black and tarry to bright red depending on the location of the tumor. With that said, tumors located in the sigmoid colon (adjacent to the rectum) may cause dark red or maroon-colored stools, while those in the rectum may result in bright red stools.14

Other symptoms of colon cancer include:13

• Diarrhea or constipation (or alternating constipation and diarrhea)

• A feeling that your bowel doesn't completely empty

• Chronic abdominal pain or cramps

• Persistent fatigue

• Persistent gas or bloating

• Unexplained weight loss

• Change in caliber of stool (pencil thin stools)

The treatment depends on the stage of cancer. It may involve surgery, radiation, chemotherapy, or immunotherapy.14

Colon Polyps

Colon polyps are growths in the large intestine. Most are benign (non-cancerous) and some can turn malignant (cancerous) over time.15

Colon polyps don't typically cause any symptoms, unless they are very large or have already turned to cancer. If symptoms do develop, they may include:16

• Blood in stools

• Changes in bowel habit

• Fatigue (generally due to anemia caused by blood loss)

• Abdominal pain (generally due to bowel obstruction)

Because colon polyps tend to cause few symptoms, they are often only found during a routine colonoscopy. To help prevent colon cancer, polyps may be removed during the colonoscopy with a procedure known as polypectomy.15

Other Causes of Stool Color Changes

Sometimes stool color can change when eating certain foods or taking certain supplements. You might confuse this with blood in the stools.

Harmless causes of stool color changes include:

• Beets

• Cranberries

• Tomatoes

• Blood sausage

• Black licorice

• Activated charcoal

• Food with red food coloring (such as strawberry gelatin)

• Bismuth found in Pepto-Bismol and Kaopectate can cause black stools

• Iron supplements can also cause black stools

What Should I Do if There's Blood in My Stool?

If you find blood in your stool or on your toilet paper or see any other evidence of rectal bleeding, call your healthcare provider and set up an appointment. Even if the cause is not serious, it is best to have that confirmed by a medical professional.

There are times, however, when you need emergency care when blood in stool is accompanied by symptoms of severe internal bleeding. If not treated immediately, a person may experience hypovolemic shock in which blood loss triggers a dangerous drop in blood pressure, leading to organ failure and death.17

Symptoms of hypovolemic shock include:18

• Dizziness or lightheadedness

• Rapid, weak pulse

• Rapid breathing

• Excessive sweating

• Blue lips (due to the loss of blood oxygen)

• Cold, clammy skin

• Confusion

• Anxiety or agitation

• Extreme weakness

• Pallor

• A feeling of impending doom

• Unconsciousness

You should also seek emergency care if rectal bleeding is profuse and continuous or if you experience bloody or coffee-ground vomit.11

Diagnosis

If you have blood in your stools, your healthcare provider will evaluate your symptoms and decide whether or not further investigation is needed.

Based on your symptoms, a review of your medical history, and a physical exam, your healthcare provider will choose which tests are most appropriate. Blood work may or may not be taken.

Direct or indirect imaging tests are commonly ordered to check for diverticular disease, colon polyps, tumors, and other causes of GI bleeding. These include:19

• Colonoscopy: A procedure used to directly view the colon with a flexible scope inserted into the rectum

• Sigmoidoscopy: A procedure used to directly view the sigmoid colon with a flexible or rigid scope inserted into the rectum

• Barium enema: An X-ray technique used to highlight the structure of the colon by delivering contrast fluid containing barium through the rectum

• Upper endoscopy: A procedure used to directly view the upper GI tract with a flexible scope inserted into the mouth

• Upper GI series: An X-ray technique, also called a barium swallow, used to highlight the structure of the upper GI tract

• CT angiography: A type of imaging test that uses a computed tomography (CT) scan and an injectable contrast dye to view your blood vessels and tissues.

Summary

Blood in the stool may be caused by a relatively minor condition or a potentially severe one. Hemorrhoids and anal fissures are two of the most common causes. Diverticular disease, inflammatory bowel disease, upper gastrointestinal bleeding, colon cancer, and colon polyps are other possible causes.

Red or black stools may also be caused by eating certain red-colored foods or taking iron supplements or Pepto-Bismol. Even so, it is important to see your healthcare provider if there is any evidence of blood in stools just to be safe.

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MedlinePlus. Rectal bleeding.

National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of hemorrhoids.

National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Disorders. Treatment of hemorrhoids.

Gardner IH, Siddharthan RV, Tsikitis VL. Benign anorectal disease: hemorrhoids, fissures, and fistulas. Ann Gastroenterol. 2020;33(1):9-18. doi:10.20524/aog.2019.0438.

National Health Service (UK). Anal fissure.

Centers for Disease Control and Prevention. What is inflammatory bowel disease (IBD)?

National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases. Treatment for Crohn's disease.

HealthLinkBC. Diverticular bleeding.

MedlinePlus. Diverticulitis.

National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases. Diverticular disease.

National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of GI bleeding.

National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases. Treatment for GI bleeding.

American Society for Gastrointestical Endocscopy. What is colorectal cancer?

Centers for Disease Control and Prevention. Colorectal (colon) cancer.

American College of Gastroenterology. Colon polyps.

MedlinePlus. Colonic polyps.

Van der Mullen J, Wise R, Vermeulen G, Moonen PJ, Malbrain MLNG. Assessment of hypovolaemia in the critically ill. Anaesthesiol Intensive Ther. 2018;50(2):141-9. doi:10.5603/AIT.a2017.0077

National Institutes of Health, U.S. National Library of Medicine: MedlinePlus. Hypovolemic shock.

Carney BW, Khatri G, Shenoy-Bhangle AS. The role of imaging in gastrointestinal bleed. Cardiovasc Diagn Ther. 2019;9(Suppl 1):S88–96. doi:10.21037/cdt.2018.12.07

Kumar AS, Ayscue J. Hematochezia and melena. In: Steele SR, Maykel JA, Wexner SD, eds. Clinical Decision Making in Colorectal Surgery. Springer International Publishing; 2020:55-63. doi:10.1007/978-3-319-65942-8_7

UCLA Health. Gastrointestinal bleeding.

American College of Gastroenterology. Lower gastrointestinal bleeding.

Additional Reading

American Cancer Society. Treatment of colon cancer, by stage.

By Barbara Bolen, PhD
Barbara Bolen, PhD, is a licensed clinical psychologist and health coach. She has written multiple books focused on living with irritable bowel syndrome.