Perhaps it is time to rethink IBS-D

To the Editor: Diarrhea predominate irritable bowel syndrome (IBS-D) currently constitutes the largest sub-category of IBS causing a significant emotional and economic impact [1]. This entity has been an enigma to physicians and an impediment to patients, interfering with the quality of life for millions of sufferers. Accordingly, physicians have been trying to clarify, categorize and attempt to understand the basis, pathophysiology and therapy for this condition without much measurable success. Different criteria have come about starting with Manning, Kruis and now up to Rome III criteria [2,3]. For most practicing primary clinical physicians and gastroenterologists, IBS-D has become a diagnosis of exclusion rather that a scientific, pragmatic work up. Recently, the American College of Gastroenterologists (ACG) published a position paper on this entity [4] in an attempt to analyze and address this condition. Although it was intended for practicing clinicians, it ended up being used primarily by researchers. In a recent large retrospective study of patients with chronic diarrhea and IBS-D [5], emphasis was placed on actual work-up and clinical outcome related to such patients. Similar to the ACG position paper, a significant number of patients can be diagnosed and treated by detailed history taking (31%). These are primarily patients complaining of carbohydrate intolerance who improved clinically with specific product abstinence, and postcholecystectomy patients who predictably responded to bile acid binding therapy. Interestingly, carbohydrate intolerance was found to be both qualitatively and quantitatively sensitive. Post-cholecystectomy diarrhea was reported to occur in the immediate post-operative period or many months later for unexplained reasons. The study, however, puts a larger emphasis on more in-depth investigations resulting in a favorable outcome in 98% of patients with an initial presentation of IBS-D. Bile-acid-related diarrhea constituted 68% of total patients. The “Habba Syndrome” [6], a syndrome associating chronic diarrhea with intact malfunctioning gallbladder, accounted for 41%of total patients in the study. As anticipated, this bile-related diarrhea responded favorably to bile acid resin therapy and showed a 98% response rate as defined by less than three bowel movements per day. The remaining patients tagged with IBS-D turned out to have other clinical conditions (see Figure 1), which, when identified and treated, resulted in a favorable outcome. If the response was partial, thena secondentitywas sought, as5%ofpatients had more than one entity contributing to their illness. Analysis of this approach led to the conclusion that IBS-D is a collection of different conditions, rather than a single entity, as the current thinking dictates. Perhaps the new approach can explain why we have been desperately trying to address this condition with unfavorable results. Perhaps our obsession with IBSD as a single entity is the problem. Furthermore, researchers have gone to the extreme, thinking that there may be an inflammatory component to IBS recommending treatment with anti-microbials [7]. We may soon find ourselves treating IBS with steroids and immunosuppressants in a desperate attempt to address this conundrum. The ACG position paper cited a higher association with IBS-D and Celiac Sprue as well as IBS-D and lactose maldigestion.