Is There a Connection Between IBS and Colitis?

Colitis is defined as inflammation in the large intestine. It can sometimes be caused by an infection (infectious colitis), but it can also be a result of an autoimmune disease (ulcerative colitis, Crohn's disease), a lack of blood supply (ischemic colitis), diverticulosis (diverticulitis), or other serious conditions.

Colitis can result in symptoms that are similar to those seen in irritable bowel syndrome (IBS). This raises the question: is there an overlap or connection between IBS and colitis? This overview will cover the more common forms of colitis and how they may or may not be related to IBS.

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IBS vs. More Serious Causes of Intestinal Symptoms

Even though IBS can significantly impair a person's quality of life, it is usually not considered a serious illness, and it will not lead to life-threatening complications. However, be sure to consult your physician if you experience any of the following symptoms that could be pointing to a much more serious condition, such as one of the forms of colitis described below.

  • Severe pain
  • Significant fatigue
  • Lack of appetite
  • New, long-lasting (greater than 6-12 weeks) constipation or diarrhea
  • Shortness of breath
  • Blood in stool
  • Change in quality of stool (new, thin, "worm-like" stools)
  • Weight loss
  • Fever
  • Mouth ulcers

IBS and IBD Compared

Two conditions that are often confused are IBS (irritable bowel syndrome) and IBD (inflammatory bowel disease). Here are the main differences between these two.


  • This is a benign condition.
  • It can cause symptoms like pain, constipation. or diarrhea.
  • It rarely places a person at risk of serious complications, surgery, or death.


  • This is a serious condition.
  • It can cause symptoms like pain, diarrhea, blood in the stool, fever, and weight loss.
  • It can lead to serious complications like bowel perforation, infection, surgery, cancer, and death.

Ulcerative Colitis and IBS

Ulcerative colitis is one of the two inflammatory bowel diseases (IBDs).

Shared Symptoms of Ulcerative Colitis and IBS

The following symptoms are shared by the two different health conditions:

Symptoms Unique to Ulcerative Colitis

Ulcerative colitis is a more serious condition than IBS. Its symptoms include:

  • Blood in the stool
  • Fever
  • Significant loss of appetite (more than can be explained by food avoidance for fear of setting off symptoms)
  • Visible signs of ulceration in the lining of the large intestine

What Causes Ulcerative Colitis?

Microscopic Colitis and IBS

Microscopic colitis is a disease in which a person experiences chronic, watery diarrhea. The disease differs from IBS in that signs of infection can be seen when intestinal cells are examined under a microscope.

Shared Symptoms of Microscopic Colitis and IBS

Symptoms Unique to Microscopic Colitis

  • Nausea
  • Weight loss

Infectious Colitis and IBS

Infectious colitis is an illness that is caused by an infectious agent, such as:

  • Campylobacter
  • Escherichia coli
  • Salmonella
  • Shigella
  • Clostridium difficile

Symptoms of Infectious Colitis

The symptoms of infectious colitis are quite different from those of IBS, and include:

  • Bloody diarrhea
  • Chills
  • Fever

Overlap Between IBD and IBS

Although the two disorders have traditionally been seen as distinct in terms of both presentation and cause, some researchers are putting forth theories that perhaps the two diagnoses of IBS and IBD are actually at different ends of the same spectrum.

Some studies have shown that people who have IBS are at higher risk of eventually being diagnosed with IBD (ulcerative colitis or Crohn's disease). One group of researchers found that this higher risk may be associated with having experienced infectious gastroenteritis (stomach "flu" caused by an infectious bacteria or virus).

Inflammation in IBS

Although the diagnosis of IBS requires that there be no visible signs of inflammation, researchers are increasingly finding evidence that inflammation does in fact play a role in the symptoms of IBS. This inflammation in the cells lining the large intestine is not visible, as is the case with ulcerative colitis, nor can it be seen with a microscope, as is the case with microscopic colitis. Instead, this inflammation is considered to be low-grade and requires an in-depth examination of tissue to identify its presence. Researchers are working to discover further information about the role of inflammation to open up the promise of more effective treatment options for IBS.

A Word From Verywell

It's imperative to monitor the signs and symptoms of IBS you may be struggling with. If you notice any significant changes, consult with your physician to ensure a more serious condition isn't brewing.

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