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Plenary III - An Integrated Approach to Irritable Bowel Syndrome
Douglas Drossman, MD
Our understanding of the irritable bowel syndrome (IBS) has changed considerably, and the pathophysiology is no longer understood in terms of any single etiology. Rather, IBS adheres to a biopsychosocial framework where the integrated effects of dysmotility, visceral hypersensitivity, inflammation with altered mucosal immunity and abnormalities in brain- gut regulation contribute to symptom generation. These effects may be mediated through neurotransmitters, including serotonin (5-HT) and cytokines (e.g., IL1-β, IL-10) or altered bacterial flora of which both may affect motility and sensation producing the bowel dysmotility and abdominal discomfort or pain of IBS.
Activation at the gut level is seen in the majority of IBS patients with mild to moderate symptoms, and psychosocial factors (e.g. anxiety, depression, coping style) alter brain-gut pathways and modulate these symptoms and the clinical outcome. Higher levels of psychosocial disturbances are seen in the smaller group of patients with more severe or more continuous pain suggesting a more prominent contribution from CNS regulatory centers.
The post-infectious IBS is an example of the relationship between psychosocial distress and altered mucosal immunity leading to the clinical features of an inflammatory subtype of IBS. Research on mucosal inflammation and immunity may help us understand the mechanisms for peripheral sensitization, while newer brain imaging techniques (e.g., PET, fMRI) may clarify the central pathways involved with the regulation of pain and its experience. Over time, as we further characterize these subgroups of IBS, newer treatments targeted to the underlying physiological determinants are likely to be developed.
The diagnosis of the FGID's involves the use of symptom-based criteria, and a conservative diagnostic approach to reduce unneeded health care costs. Treatment begins with an effective physician-patient relationship and then includes treatment modalities that are targeted both to the nature (e.g. diarrhea or constipation) and the severity (e.g. pain, disability) of the symptoms. These may include gut related agents (e.g. affecting motility or visceral sensitivity) or modalities targeted toward CNS regulation of GI symptoms (e.g. CBT, hypnosis, psychopharmacological agents).