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Irritable bowel syndrome or inflammatory bowel disease: What’s the difference?

Raymond Lepage, PhD
Raymond Lepage, PhD
Senior Scientific Advisor

What are the main distinctions between the two conditions?

The main difference between irritable bowel syndrome (IBS) and chronic inflammatory bowel disease (IBD) is, in the case of IBS, the absence of inflammation in the digestive tract. Inflammation is a defence mechanism of the body against all kinds of attacks: the presence of foreign bodies (e.g., viral, bacterial or parasitic infections, cancer or tissue graft cells, allergens, etc.) or traumas (including “everyday” traumas such as joint injuries and those caused by surgery or burns). In the case of so-called “autoimmune” disorders, the defence system goes awry and begins considering normal components of the body as foreign invaders. Crohn’s disease and ulcerative colitis are very likely caused by an inappropriate immune response to bacteria normally found in the digestive tract.

White blood cells to the rescue

The inflammatory response involves the mobilization of white blood cells at the site of the attack. This phenomenon is sometimes even visible to the naked eye in the form of pus around a foreign body such as a splinter: the whitish liquid contains, among other things, a very large number of white blood cells (also called neutrophils). In the case of an inflammatory response in the digestive tract, neutrophils invade the affected portion of the intestinal mucosa. These white blood cells, and the extent of the damage they cause, can be identified when examining a biopsy of the intestinal wall usually obtained during a colonoscopy.

When neutrophils are present at the site of inflammation, they release a series of specific markers, including a protein called calprotectin. These markers can be detected in the blood, indicating presence of an inflammatory process in the body, but cannot specify which organ is affected. This is not the case with inflammatory bowel diseases, as the presence of these markers can be

identified directly from a stool sample! The presence of significant amounts of calprotectin in a stool sample is a sure sign that neutrophils (and, therefore, inflammation) are present in the intestinal wall. If you have inflammation, your doctor will prescribe additional tests (colonoscopy, etc.) to determine the cause and nature of this inflammation. In the absence of calprotectin (and, consequently, inflammation), and taking into account other criteria (see list below), your doctor may conclude that you most likely have irritable bowel syndrome and adjust your medical follow-up accordingly.

What symptoms are not consistent with IBS?

This is a list of conditions or symptoms incompatible not consistent with a diagnosis of IBS:

  • Onset of symptoms after age 50
  • Severe or gradually worsening symptoms
  • Unexplained weight loss
  • Nocturnal diarrhea
  • Family history of gastrointestinal diseases (colon cancer, celiac disease and inflammatory bowel disease)
  • Rectal bleeding or melena (black stools)
  • Unexplained iron deficiency anemia

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