When the inflammation settles and the symptoms do not

Remission is a statement about inflammation. It says the tests used to look for active disease — a scope, a scan, a stool test — did not find much of it. It is not a statement about how the bowel feels, and for a large minority of people the two part company.

A 2026 review in the Journal of Clinical Medicine puts the pooled figure at 32.5 percent, with a 95 percent confidence interval of 27.4 to 37.9: roughly one in three people with quiescent inflammatory bowel disease — quiescent meaning no endoscopic evidence of active inflammation — nonetheless have symptoms that meet the criteria for irritable bowel syndrome. It is more common in Crohn’s disease than in ulcerative colitis.

It is not a new observation. Whorwell and colleagues reported in 1983 that 33 percent of people with ulcerative colitis in remission met the symptom criteria for irritable bowel syndrome. Four decades later the figure has barely moved.

The number moves with the instrument

Here is the part worth carrying around, because it explains why you will see this quoted as a quarter in one place and over a third in another. The prevalence depends on how remission was established in the first place, and the three usual ways do not agree:

• endoscopy, the closest thing to a gold standard for looking at the lining of the bowel: 23.5 percent
• disease activity indices, the scored questionnaires: 33.6 percent
• faecal calprotectin, the stool test: 35.1 percent

One phenomenon, three answers, and the spread between them is not noise. The closer the look at the bowel wall, the more of those symptoms turn out to be inflammation after all. The looser the test, the more people are counted as being in remission, and the more symptoms are left over with nothing to pin them on.

What a calprotectin can and cannot say

Faecal calprotectin measures neutrophils — white blood cells — moving into gut tissue, which is why it tracks inflammation rather than discomfort. Its accuracy depends entirely on where the line is drawn. One meta-analysis found the best sensitivity, 90.6 percent, above 50 micrograms per gram, and the best specificity, 78.2 percent, above 100. The American Gastroenterological Association uses a cut-off of 150 micrograms per gram when deciding whether someone’s symptoms reflect a flare of Crohn’s disease or ulcerative colitis.

The order the questions come in

None of this makes symptoms in remission a first assumption. A relapse of the disease should always be the first consideration when bowel function is acutely disturbed, and after that the review lists causes that are nothing to do with inflammation at all — adhesions, kidney or gallbladder stones, an abscess.

For symptoms that are chronic rather than sudden there is a second list, and it is specific to this disease rather than borrowed from general gut medicine. Disease in the ileum, or a resection of it, makes bile acid malabsorption more likely. Small bowel Crohn’s disease raises the risk of small intestinal bacterial overgrowth. Coeliac disease is also in the frame. Each of the three can look like irritable bowel syndrome from the outside, and each has its own test and its own treatment.