IBS-type symptoms in patients with IBD are probably caused by occult inflammation and are not the result of true IBS, according to the findings of a new study by Fergus Shanahan and colleagues from University College Cork in Ireland.

The familiar appearance of aphthous ulceration at colonoscopy, confirming unsuspected active Crohn's disease in a patient thought to be in remission but complaining of IBS-type symptoms. Colonoscopy was prompted by the finding of elevated fecal calprotectin levels. Courtesy of F. Shanahan.

IBS-type symptoms are commonly reported in patients with IBD and the prevalence of both diseases in the general population means that it is statistically possible for patients with IBD to have IBS. However, proving that IBS and IBD coexist is problematic because the two diagnoses are mutually exclusive. Even in patients who have IBD that is in remission it is difficult to evaluate IBS-type symptoms—it is not possible to be sure that the disease really is in remission and that no inflammation is present without performing exhaustive and invasive tests.

“To approach this [problem],” explains Shanahan, “we selected patients with IBD who were considered by their physician to be in remission by conventional clinical criteria and who fulfilled predefined criteria of remission.” 106 patients (62 with Crohn's disease and 44 with ulcerative colitis) were recruited. The authors then assessed the prevalence of IBS-type symptoms and used a non-invasive test—the measurement of fecal calprotectin levels—to look for evidence of occult gastrointestinal inflammation.

“The study confirmed that IBS-type symptoms are common in patients with IBD, even those who are thought to be in clinical remission,” reports Shanahan. Indeed, almost 60% of patients with Crohn's disease and 40% of patients with ulcerative colitis had symptoms that fulfilled Rome II criteria for IBS.

Shanahan goes on, “The most important finding was that when we looked at fecal calprotectin we found that the highest levels of calprotectin were in the patients with IBS-type symptoms compared with healthy controls and those patients without IBS-type symptoms.”

This finding means that the IBS-type symptoms reported in patients with IBD that is thought to be in remission actually reflect ongoing IBD activity. If gastrointestinal symptoms in these patients are inappropriately attributed to IBS instead of occult inflammation then anti-inflammatory treatment may be delayed and the risk of complications enhanced.

So, what do the findings of this study mean for clinical practice? “The main implication of the work is that symptomatic patients [with IBD] should always be evaluated for treatable inflammation,” says Shanahan. “IBD is IBD unless proven otherwise.” Basic and clinical investigators are now working together to study the relationship between minimal or occult inflammation and the genesis of symptoms.