Although visceral hypersensitivity is considered a hallmark feature of IBS, conflicting evidence exists regarding somatic hypersensitivity in this patient population. Several investigators have found no evidence for heightened somatic pain sensitivity in IBS patients. Also, others have reported similar cold presser pain tolerance in IBS patients and controls. These conflicting findings may result from differing somatic pain testing procedures.
Previous studies have explored the correlates of visceral hypersensitivity among patients with IBS. To further evaluate somatic hyperalgesia among patients with IBS, the authors evaluated thermal pain sensitivity among patients with diarrhea-predominant IBS (D-IBS) vs constipation-predominant IBS (C-IBS) compared with healthy subjects.
A research led by G Nicholas Verne from United States addressed this issue. The article is to be published on July 14, 2009 in the World Journal of Gastroenterology. A total of 42 cases with D-IBS and 24 with C-IBS, and 52 control subjects were collected in the study. Their thermal pain hypersensitivity were examined Thermal stimuli were delivered using a Medoc Thermal Sensory Analyzer with a 3 cm × 3 cm surface area. Heat pain threshold (HPTh) and heat pain tolerance (HPTo) were assessed on the left ventral forearm and left calf using an ascending method of limits. The Functional Bowel Disease Severity Index (FBDSI) was also obtained for all subjects.
The research revealed controls were less sensitive than C-IBS and D-IBS with no differences between C-IBS and D-IBS for HPTh and HPTo. Thermal hyperalgesia was present in both groups of IBS patients relative to controls, with IBS patients reporting significantly lower pain threshold and pain tolerance at both test sites.
A unique finding of this study is that the authors detected a strong relationship between heat pain measures and Functional Bowel Disease Severity Index (FBDSI) scores. IBS patients with high FBDSI scores had the highest thermal pain sensitivity compared to those IBS patients with low to moderate FBDSI scores.
- Zhou Q, Fillingim RB, Riley JL, Verne GN. Thermal hypersensitivity in a subset of irritable bowel syndrome patients. World J Gastroenterol, 2009; 15(26): 3254-3260 [link]
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