Is There a Connection Between IBS and Colitis?

Colitis is defined as inflammation in the large intestine. It can be caused by many things, including:

  • Infection (infectious colitis)
  • Immune-mediated disorders (ulcerative colitis, Crohn's disease)
  • Lack of blood supply (ischemic colitis)
  • Diverticulosis (diverticulitis)
  • Other serious conditions

Colitis can result in symptoms that are similar to those of irritable bowel syndrome (IBS). This raises the question: Is there an overlap or connection between IBS and colitis?

Woman sick in bed
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IBS vs. More Serious Causes of Intestinal Symptoms

Even though IBS can significantly impair your quality of life, it is usually not considered a serious illness, and it doesn't lead to life-threatening complications.

However, be sure to talk to your healthcare provider if you experience any symptoms that could point to a more serious condition, including:

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

Ulcerative Colitis and IBS

Ulcerative colitis is one of the two inflammatory bowel diseases (IBDs). Symptoms shared by ulcerative colitis and IBS include:

Ulcerative colitis is a more serious condition than IBS. Other symptoms of ulcerative colitis that aren't present in IBS 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
  • Skin rash
  • Red eye
  • Vision changes
  • Joint pain

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 inflammation can be seen when intestinal cells are examined under a microscope.

Shared symptoms of microscopic colitis and IBS are:

Weight loss is a symptom that is unique to microscopic coliti.:

Infectious Colitis and IBS

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

  • Campylobacter
  • Escherichia coli
  • Salmonella
  • Shigella
  • Clostridioides difficile

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).

  • Benign

  • Symptoms: pain plus constipation and/or diarrhea

  • Rarely leads to serious complications, surgery, or death

  • Can be serious

  • Symptoms: pain, diarrhea, bloody stool, fever, weight loss, fatigue

  • Can lead to bowel perforation, infection, surgery, cancer, and death

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 or any other digestive disorder you may be struggling with. If you notice any significant changes, talk to your healthcare provider and get tested so you can treat the problem and feel better.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Chira A, Chira RI, Dumitrascu DL. Inflammation as a potential therapeutic target in IBS. In: Irritable Bowel Syndrome - Novel Concepts for Research and Treatment. InTech; 2016. doi:10.5772/66193.

  2. Lynch WD, Hsu R. Ulcerative Colitis. In: StatPearls [Internet].

  3. Gentile N, Yen EF. Prevalence, pathogenesis, diagnosis, and management of microscopic colitis. Gut Liver. 2018;12(3):227–235. doi:10.5009/gnl17061

  4. Ingle SB, Adgaonkar BD, Ingle CR. Microscopic colitis: Common cause of unexplained nonbloody diarrhea. World J Gastrointest Pathophysiol. 2014;5(1):48–53. doi:10.4291/wjgp.v5.i1.48

  5. Azer SA, Tuma F. Infectious colitis. In: StatPearls [Internet].

  6. Papaconstantinou HT, Thomas JS. Bacterial colitis. Clin Colon Rectal Surg. 2007;20(1):18-27. doi:10.1055/s-2007-970196

Additional Reading

By Barbara Bolen, PhD
Barbara Bolen, PhD, is a licensed clinical psychologist and health coach. She has written multiple books focused on living with irritable bowel syndrome.