Bloody Stool: Causes

By McBratney, Susan PhD
By Spader, Catherine RN

What causes bloody stool?

Blood in the stool can indicate a relatively mild condition, such as hemorrhoids or constipation, or it can be due to a serious, even life-threatening condition, such as esophageal varices or colon cancer. Certain medications, such as aspirin, can also cause bloody stool.

Black, tarry stools usually indicate that the blood is coming from the upper gastrointestinal tract (esophagus, stomach and duodenum), while red or maroon-colored stools often originate from bleeding in the lower gastrointestinal tract (colon, rectum and anus). Bloody stool that is associated with dizziness, diarrhea, or vomiting blood should be immediately evaluated in an emergency setting. However, a diagnosis of the cause of blood in the stool can be delayed or missed because tiny amounts of blood may not be noticeable for long periods of time.

Upper gastrointestinal tract causes of bloody stool

Causes of bloody stool related to the upper gastrointestinal tract include:

  • Bleeding peptic ulcer

  • Blood vessel malformation

  • Esophageal trauma

  • Esophageal varices

  • Gastritis

  • Gastroenteritis

  • Stomach cancer

  • Stomach varices

  • Swallowed blood from nosebleed

Lower gastrointestinal tract causes of bloody stool

Causes of bloody stool related to the lower gastrointestinal tract include:

  • Anal fissure

  • Anal sex

  • Blood vessel malformation

  • Bowel ischemia or bowel obstruction

  • Colon cancer

  • Constipation

  • Diverticulosis

  • Gastroenteritis

  • Hemorrhoid

  • Inflammatory bowel disease (Crohn’s disease or ulcerative colitis)

  • Intestinal infection (food poisoning)

  • Intestinal polyps or intestinal tumor

  • Meckel’s diverticulum (an abnormal pouch near the lower end of the small intestine)

  • Rectal prolapse

Other causes of bloody stool

Bloody stool can be caused by:

  • Medication side effects

  • Radiation therapy

Serious or life-threatening causes of bloody stool

Any type of blood in the stool should be evaluated by a health care professional. In some cases, bleeding may accompany a serious or life-threatening condition including:

What are the potential complications of bloody stool?

Over time, bloody stool can lead to serious complications including:

  • Anemia

  • Severe blood loss

  • Shock 


What is bloody stool?

Blood in the stool is an abnormal, potentially critical condition in which there is blood mixed in with a bowel movement or feces. The blood can arise from anywhere along the digestive tract, from the mouth to the anus. Bloody stool is often a sign of gastrointestinal bleeding due to injury or disease. Stools that contain bright red or maroon-colored blood may be referred to as hematochezia, wh... Read more about bloody stoolintroduction


What other symptoms might occur with bloody stool?

Depending on the underlying disease, disorder or condition, bloody stool may occur with other symptoms including:

Medical Reviewer: Cynthia Haines, MD Last Annual Review Date: Jul 31, 2013 Copyright: © Copyright 2014 Health Grades, Inc. All rights reserved. May not be reproduced or reprinted without permission from Health Grades, Inc. Use of this information is governed by the HealthGrades User Agreement.

This Article is Filed Under: Digestive System, Ulcerative Colitis

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