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Blood in Stools - Causes, Diagnosis, and Treatment

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Blood in the stool, known as hematochezia, indicates bleeding in the gastrointestinal tract. Read the article to know more about blood in the stool.

Written by

Dr. P. Saranya

Medically reviewed by

Dr. Ghulam Fareed

Published At December 7, 2022
Reviewed AtJune 8, 2023


Blood in the stool is caused due to a variety of causes which indicates bleeding in the gastrointestinal tract. Bleeding can occur anywhere in the digestive tract, from the mouth to the anus. Blood in the stool can have two colors. Usually, the blood in the stool looks blood-red or maroon. But when bleeding is caused in the upper digestive tract, the blood looks black and tarry, called melena. Blood in the stool may indicate an underlying condition and should never be ignored. Upper gastrointestinal bleeding is more common than lower intestinal bleeding.

What Are the Causes of Blood in the Stool?

Many reasons that cause blood in the stool.

The possible causes include:

  • Peptic Ulcers: Ulcers look like sores in the digestive tract lining caused by Helicobacter pylori infection. Blood from peptic ulcer disease looks red, or it can be black or tarry.

  • Hemorrhoids: Hemorrhoids are swollen blood vessels that bulge from the anus. It is painful and uncomfortable, and hemorrhoids cause bright red blood in the stool.

  • Anal Fissures: Anal fissures are caused by constipation and harder stools that cannot pass. Anal fissures are small cuts or tears in the lining of the anus that look like a crack in the skin of the anus. Anal fissures can cause blood in the stool, which is bright red.

  • Colon Polyps: Colon polyps are small growths in the lining of the large intestine. Colon polyps have a high tendency to develop into colorectal cancer. Polyps usually show no symptoms, but they cause blood in the red or black stools.

  • Gastroenteritis: Gastroenteritis is the inflammation of the stomach and intestine, which is caused by infection by bacteria, viruses, or parasites. Food allergies can also cause gastroenteritis. Bloody diarrhea is a common symptom of gastroenteritis.

  • Angiodysplasia: Angiodysplasia occurs when the blood vessels in the digestive system weaken. Angiodysplasia is common during end-stage renal disease or kidney failure. It causes blood in the stool.

  • Inflammatory Bowel Disease: Ulcerative colitis and Crohn's disease are the most common forms of inflammatory bowel disease. It is an autoimmune condition in which the body attacks its healthy cells, causing inflammation of the intestines. Symptoms of this disease include bloody stools, which are red or tarry.

  • Colorectal Cancer: Cancers can cause blood in the stool, which is red or black, or tarry.

  • Diverticulitis: Diverticula are abnormal pouches formed in the lower intestine. When the diverticula is inflamed, it causes diverticulitis which causes red or maroon stools.

  • Colon Ischemia: Colon ischemia occurs when the blood supply to the large intestine is blocked or reduced. They cause diarrhea and red blood in the stool.

  • Food Colors: Sometimes, dyes and coloring products used in the foods can give a red color to the stool, which imitates bloody stools.

  • Medications: Bloody stool can be a side effect of some blood-thinning medications like Warfarin and Enoxaparin.

What Are the Diagnostic Tests for Blood in Stools?

The doctor will ask about the symptoms and inquire about the color of the blood and how much blood was visible in the stool to diagnose the cause of the condition.

The following tests are done for the diagnosis of bloody stools:

  • Blood Test: Complete blood count is taken to determine the extent of blood loss.

  • Fecal Occult Blood Test: A stool sample is collected and analyzed in the laboratory for the presence of blood.

  • Digital Exam: A rectal examination is done to determine the causes of bleeding associated with rectum-like hemorrhoids.

  • Nasogastric Lavage: This test can determine whether the upper or lower digestive tract is causing the bleeding. A tube is inserted through the nose into the stomach, and the contents of the stomach are removed. If the stomach does not contain any blood, the blood in the stool is mostly due to lower digestive tract problems.

  • Endoscopy: A small, thin, flexible tube attached to a camera is inserted through the mouth into the stomach and intestine to view the cause of bleeding. An endoscope is also used to take tissue samples (biopsy) for examination in the laboratory.

  • Colonoscopy: A long, thin, flexible tube attached to a camera is inserted through the rectum into the colon, which can view the entire colon and rectum. It has a long tube compared to an endoscope and is also used to take tissue samples for microscopic examination.

  • Barium X-Ray: The patient is asked to drink a liquid containing barium which coats the lining of the digestive tract, and x-rays are taken. Barium is also inserted into the rectum as an enema.

  • Enteroscopy: This procedure uses an endoscope to view the small intestine. Capsule enteroscopy involves swallowing a capsule with a tiny camera that can show images of the intestine as it passes through the digestive tract.

  • Computed Tomography (CT) Angiography: In this procedure, a dye is injected into the blood vessels, and a computed tomography scan is taken. The dye leaks out from the bleeding site and is easily seen on the scan.

How Can We Treat Blood in the Stool?

Treatment is focused on stopping the bleeding from the digestive tract and managing the cause of the bleeding. Cauterization or laser is done during an endoscopy procedure to stop bleeding from the vessel. Angiography is used to inject medicines into the bleeding vessel.

Depending on the cause, the following treatments are recommended to treat the cause of the bloody stools:

  • Suppose a peptic ulcer is causing the bloody stool. In that case, antibiotics are given to treat Helicobacter pylori infection, and proton pump inhibitors and H2 receptor blockers are provided to suppress the acid production.

  • In the case of ulcerative colitis, anti-inflammatory drugs are given.

  • Surgery is indicated in the case of colon polyps or colorectal cancer.

  • In the case of hemorrhoids and anal fissures, eating a high-fiber diet and taking a sitz bath can reduce the symptoms.


Blood in the stool is not always serious, but mostly, it can be due to an underlying medical condition. Sometimes, it is harmless and can heal on its own. However, identifying the cause of the bleeding can help in immediate treatment and better outcomes.

Dr. Ghulam Fareed
Dr. Ghulam Fareed

Medical Gastroenterology


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