Merck Manual

Please confirm that you are not located inside the Russian Federation


Hemorrhagic Colitis


Thomas G. Boyce

, MD, MPH, University of North Carolina School of Medicine

Last full review/revision Jun 2019| Content last modified Jun 2019
Click here for the Professional Version
NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Topic Resources

Hemorrhagic colitis is a type of gastroenteritis in which certain strains of the bacterium Escherichia coli infect the large intestine and produce a toxin (Shiga toxin) that causes bloody diarrhea and other serious complications.

  • Hemorrhagic colitis can be caused by toxins produced by Escherichia coli.

  • Organisms that cause the disorder are usually acquired from contaminated ground beef or water or unpasteurized milk.

  • Abdominal cramps and diarrhea that may be bloody are the usual symptoms.

  • The diagnosis is based on a doctor's evaluation and the results of stool tests.

  • Preventive measures include thorough cooking of meat and thorough washing of hands.

  • Treatment involves drinking plenty of fluids.

Hemorrhagic colitis can occur in people of all ages but is most common among children and older people. There are many strains of Escherichia coli (E. coli) that cause hemorrhagic colitis. In North America, the most common strain is E. coli O157:H7. These bacteria naturally occur in the intestines of about 1% of healthy cattle. Outbreaks can be caused by eating undercooked ground beef or by drinking unpasteurized milk or juice. Consuming food or water contaminated with cow manure or raw ground beef can also spread the infection. The disease can be transmitted from person to person, particularly from children in diapers to other people. Inadequately chlorinated recreational water parks can be a source of infection.

E. coli toxins damage the lining of the large intestine. If the toxins enter the bloodstream, they can also affect other organs, such as the kidneys.


Severe abdominal cramps begin suddenly along with watery diarrhea, which may become bloody within 24 hours. The diarrhea usually lasts 1 to 8 days. Fever is usually absent or mild but occasionally can exceed 102° F (39° C).

About 5 to 10% of people with hemorrhagic colitis develop a severe complication called hemolytic-uremic syndrome. Symptoms include a low red blood cell count (anemia, characterized by fatigue, weakness, and pale skin color) caused by the destruction of red blood cells (hemolytic anemia), a low platelet count (thrombocytopenia), and sudden kidney failure. Some people with hemolytic-uremic syndrome also develop complications of nerve or brain damage, such as seizures or strokes. Hemolytic-uremic syndrome typically develops in the second week of illness, sometimes preceded by an increasing fever. Hemolytic-uremic syndrome is more likely to occur in children under age 5 years and in people over age 60. Even without hemolytic-uremic syndrome and its complications, hemorrhagic colitis may cause death in older people.


  • Stool tests

A doctor usually suspects hemorrhagic colitis when a person has bloody diarrhea. To make the diagnosis of hemorrhagic colitis, a doctor has stool specimens tested for strains of E. coli or the toxins they produce.

Other tests, such as sigmoidoscopy, may be done if a doctor suspects that other diseases may be causing the bloody diarrhea.


  • Thorough cooking of meat

  • Hygiene

Improved meat-processing procedures in the United States have helped reduce the rate of meat contamination with E. coli. Despite these measures, ground beef can still be contaminated. Thus, ground beef should be cooked to an internal temperature of 160° F (71° C) or until juices run clear. People should drink only pasteurized milk and milk products.

People should properly dispose of the stool of infected people, practice good hygiene, and wash their hands with soap to limit the spread of infection. Children should no longer have diarrhea and should have two negative stool tests before they are allowed to return to the child care center.

People should report outbreaks of bloody diarrhea to public health authorities, because intervention can prevent infection in other people. Reporting can be done by contacting the local county Department of Health via information found on the web site or in the phone book.


  • Drinking fluids

  • Sometimes fluids by vein

The most important aspect of hemorrhagic colitis treatment is drinking enough fluids. Sometimes so much fluid is lost, however, that a doctor has to replace fluids by vein (intravenously). Antibiotics are not given because they actually increase the risk of developing hemolytic-uremic syndrome. The disorder eventually goes away on its own.

People who develop complications are likely to require intensive care in the hospital and may need kidney dialysis and other specific treatment.

Did You Know...

  • Antibiotics are not given for hemorrhagic colitis suspected to be caused by E. coli because they do not lessen symptoms, they do not prevent spread of the infection, and they actually increase the risk of developing hemolytic-uremic syndrome.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Also of Interest


View All
The Stomach
The Stomach
3D Models
View All
Crohn Disease
3D Model
Crohn Disease