Multidimensionality of symptom complexes in irritable bowel syndrome and other functional gastrointestinal disorders

The definition of irritable bowel syndrome (IBS) by Rome criteria was a major advancement in the nosology of the disease, but this goal was achieved by employing symptoms related to the gastrointestinal tract and by eliminating all symptoms that were nonspecific. The description of the course of the illness and response to treatment has been hampered by restrictions to the defining characteristics, abdominal pain and altered bowel habit. Other abdominal symptoms (e.g., bloating, nausea, and epigastric discomfort) and general somatic symptoms (e.g., fatigue, headache, and sleep disturbance) are not included in the Rome definition, yet are commonly reported by patients with IBS. This article addresses the following questions: Are comorbid conditions part of or distinct from the syndrome of IBS and other functional gastrointestinal disorders (FGIDs)? Are there overlapping abdominal or extra-abdominal symptoms confounding the definition of IBS? Are extra-abdominal somatic symptoms and/or syndromes part of the clinical presentation of IBS? Are "nondiagnostic" abdominal symptoms important in defining symptom burden in IBS? Is the concept of somatization related to IBS, and, if so, how? How can we better define the symptom burden in IBS and other FGIDs? In short, have we hampered the evaluation of IBS (and other FGIDs) by making the definitions too reductionist? While definite answers to the above questions are not possible at this time, this article proposes that the definitions of IBS or other FGIDs not be altered, but that in the process of evaluation of the clinical end points and/or severity of the diseases, consideration be given to the possibility of including other components of the symptom burden of these disorders.