Research Description:

Pain Perception in Patients with Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder that is estimated to affect 20 percent of the United States population. Symptoms include chronic abdominal pain and altered bowel function (diarrhea and/or constipation). Currently, treatment methods for patients suffering from IBS are limited, largely due to the unknown pathophysiology of the condition. The majority of IBS patients display visceral hypersensitivity (i.e., decreased pain thresholds in response to gut distension). Recent evidence has shown that patients with IBS also experience somatic hypersensitivity from experimental thermal pain stimuli. These findings are contradictory to previous data that suggested hypersensitivity due to IBS is limited to the gut.

To clarify this discrepancy, we plan to study 20 IBS patients and 20 controls to assess differences in perceptual responses using four well-validated experimental somatic pain stimuli (thermal pain, pressure pain, cold pressor pain, ischemic pain). It is hypothesized that IBS patients will display hypersensitivity to all four experimental pain stimuli. In addition, we anticipate greater hypersensitivity for deep, tonic stimuli (e.g. ischemic pain) than for superficial, brief stimuli (e.g. thermal pain).

Little is known about both the pathophysiology of IBS and the mechanisms that lead to chronic visceral hypersensitivity among IBS patients. Therefore, differences in experimental pain responses between controls and IBS patients could not only assist in diagnosis of IBS but more importantly lead to a better understanding of the effects of such a common disorder on the nervous system, specifically central sensitization. This would ultimately provide more insight into the pathophysiology of this disorder. Furthermore, identification of novel treatment methods may be possible with the discovery of somatic hypersensitivity in patients. To date, no research has been done to systematically characterize perceptual and physiological pain response to multiple somatic pain stimuli among IBS patients.