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What Can Cause Bloody Diarrhea?

Reviewed by Sabrina Felson, MD on December 11, 2019

It’s unpleasant to have diarrhea by itself, so it’s understandable to be concerned if you find blood in it. Loose, watery stool with bleeding can be a symptom of a serious condition like ulcerative colitis or a bacterial infection.

No matter what the cause is, your doctor has treatments that can help, so call them right away. Don’t try to treat it on your own with anti-diarrheal meds. In some cases, that could make things worse.

Your doctor will figure out what’s going on and prescribe the right medicine for you. They’ll also make sure that you don’t lose too many important fluids and minerals, which can be dangerous.

Here are some of the conditions that can bring on this symptom.

Inflammatory Bowel Disease (IBD)

If you have bloody diarrhea that goes on for weeks, IBD might be the reason why. This long-term condition inflames parts of your digestive tract. Experts aren’t sure exactly why that happens.

There are two main kinds of IBD: ulcerative colitis and Crohn’s disease.

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Ulcerative colitis. This condition affects your colon and rectum. One of the most common symptoms is diarrhea with blood or pus.

Other signs are:

Treatments for ulcerative colitis include:

Crohn’s disease. This type of IBD can affect any section of your digestive tract, from your mouth to your anus. Diarrhea is a common symptom. If the disease affects only your small intestine, you’re more likely to have watery diarrhea. Sometimes it causes rectal bleeding.

You may also have:

  • Belly cramps and pain
  • Weight loss
  • Fever
  • Mouth sores

Treatments for Crohn’s include:

  • Medication
  • Changes to what you eat
  • Surgery

Ischemic Colitis

This is when blood flow to your colon slows down or stops. The lack of oxygen causes damage to your intestine.

The blockage can happen slowly over time, such as when cholesterol builds up in your arteries. Or it can happen all of a sudden from a blood clot or from a serious drop in your blood pressure.

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It can lead to bloody diarrhea. It usually also comes with abdominal pain that can be mild or serious.

You may also have symptoms like:

  • Bloating
  • Fever
  • Nausea or vomiting
  • Urgent need to go to the bathroom

Treatments for it can include:

Bacterial Infections

Bloody diarrhea from IBD can last for a while if you don’t treat it. If it’s from a bacterial infection, it doesn’t usually last more than 2 weeks. It doesn’t come back after it gets better, unless you catch the same infection again.

Bacterial infections that can cause bloody diarrhea include:

E. coli. It can taint food, water, and unwashed hands -- and if you put any of those in your mouth, you could get sick. Some strains of E. coli in particular, called “STEC,” make a toxin that can trigger bloody diarrhea.

Other symptoms of a STEC infection:

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There’s no specific treatment. Antibiotics might make it worse. Your doctor may tell you to drink plenty of fluids and get lots of rest.

Salmonella. It’s common for this bacteria to make you sick through food poisoning, yet the food may look and smell fine.

An infection can give you bloody diarrhea as well as other symptoms like:

  • Fever
  • Stomach cramps
  • Nausea or vomiting
  • Headache

Treatment for serious salmonella include antibiotics and hospital care.

Shigella. This tends to spread through fouled food or water and hand-to-mouth contact. You may be more likely to catch it if you travel to a developing country.

Sometimes it brings on bloody diarrhea. You may also have:

  • Fever
  • Stomach pain
  • An urge to go to the bathroom even though you don’t need to

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Treatment includes:

  • An antacid medication like bismuth subsalicylate
  • Antibiotics

Campylobacter. This bacteria makes about a million and a half people sick each year in the U.S., but you may be more likely to get infected by it if you travel abroad. In most cases, it’s the result of eating raw or undercooked poultry or another food that touched it.

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The diarrhea that can come with it is usually bloody. It can also give you symptoms like:

  • Fever
  • Belly cramps
  • Nausea or vomiting

Treatments include:

  • Antibiotics
  • Extra fluids

You can take steps to lower your odds of getting a bacterial infection that could give you bloody diarrhea:

  • Wash your hands often, especially after you touch other people or animals.
  • Cook meat all the way through. Keep it away from other foods.
  • Wash any surfaces and utensils that raw meat touches.
  • Don’t buy raw milk or unpasteurized foods or drinks.
  • Try not to swallow water from lakes, ponds, or swimming pools.
  • If you travel to places that don’t always have safe water, make sure to eat only cooked foods. Drink only bottled drinks from unopened bottles. Stay away from ice and unpeeled fruits and veggies.

Other Causes

A couple of conditions that are less likely to trigger diarrhea with rectal bleeding are colon cancer and polyps. Also, radiation therapy for advanced stomach cancer can cause diarrhea, while bleeding may be due to the disease itself.

WebMD Medical Reference

Sources

SOURCES:

American College of Gastroenterology: “Diarrheal Diseases: Acute and Chronic,” “Colon Ischemia.”

American Cancer Society: “Radiation Therapy for Stomach Cancer,” “Colorectal Cancer Signs and Symptoms.”

CDC: “What is inflammatory bowel disease (IBD)?” “E. coli (Escherichia coli): Questions and Answers,” “Salmonella,” “Shigella – Shigellosis," “Campylobacter (Campylobacteriosis).” Crohn’s & Colitis Foundation: “Crohn's Disease Treatment Options.”

Health Technology Assessment: “Faecal calprotectin testing for differentiating amongst inflammatory and non-inflammatory bowel diseases: systematic review and economic evaluation.”

Cleveland Clinic: “Colon Polyps,” “Diarrhea,” “Ulcerative Colitis: Management and Treatment,” “E. coli Infection: Management and Treatment.”

WomensHealth.gov: “Inflammatory bowel disease.”

National Institute of Diabetes and Digestive and Kidney Diseases: “Ulcerative Colitis,” “Symptoms & Causes of Crohn’s Disease.”

Up to Date: “Causes of acute infectious diarrhea and other foodborne illnesses in resource-rich settings,” “Approach to the adult with acute diarrhea in resource-rich settings,” “Colonic ischemia.”

Johns Hopkins Medicine: “Diarrhea.”

Mayo Clinic: “Ischemic Colitis.”

Gastroenterologia Japonica: “Lower gastrointestinal bleeding in inflammatory bowel disease.”

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