Distinctive Features of Postinfective Irritable Bowel Syndrome

Laurie Barclay, MD

July 25, 2003

July 25, 2003 — Patients with postinfective irritable bowel syndrome (PI-IBS) have more diarrheal symptoms, fewer psychiatric symptoms, and a greater increase in serotonin-containing enterochromaffin (EC) cells than those whose IBS did not start after an infectious disease, according to the results of a study published in the July issue of the American Journal of Gastroenterology. The investigators speculate that subclassifying patients may allow for better and more specific therapies for some patients with IBS.

"IBS patients are heterogeneous, both in symptoms and in etiology, and progress in understanding pathogenesis has been limited for lack of objective measures to allow meaningful subdivision," write Simon P. Dunlop, MSc, from University Hospital in Nottingham, U.K., and colleagues. "Recently there has been progress in defining one subgroup of patients, i.e., those developing IBS symptoms after an episode of infective gastroenteritis."

In this study, 75 consecutive IBS outpatients and 36 healthy controls completed a questionnaire and had a full diagnostic workup including rectal biopsy. Of the 75 patients with IBS, 23 had onset of symptoms after an infectious illness and 52 did not.

Predominance of diarrhea occurred in 70% of PI-IBS patients and in 42% of non–PI-IBS patients (P = .03), and previous treatment for anxiety or depression occurred in 26% of PI-IBS patients and in 54% of the non–PI-IBS group (P = .02).

Using conventional criteria, biopsy results for all patients were normal, but there were increased EC cells in the PI-IBS group compared with the non–PI-IBS group (P = .017) and with controls (P = .02). Lamina propria T lymphocytes were increased in PI-IBS (P = .026) and in non–PI-IBS (P = .011) patients compared with control patients, and mast cells were increased in non–PI-IBS patients (P = .054) compared with control patients.

The authors do not recommend rectal biopsy in all patients, but they note that "these group differences are important, as they suggest that different types of IBS may have different pathogenic mechanisms. By defining different 'key players' such as mast cells, lymphocytes, and EC cells, they suggest new specific pharmacological targets for therapy. They also suggest new objective measures such as plasma serotonin or serum tryptase with which we can seek to subclassify IBS and to identify those individuals who will respond to specific therapies."

AstraZeneca supported this work through an educational grant.

Am J Gastroenterol. 2003;98:1578-1583

Reviewed by Gary D. Vogin, MD

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