Thermal and visceral hypersensitivity in irritable bowel syndrome patients with and without fibromyalgia

Background: Irritable bowel syndrome (IBS) is a chronic gastrointestinal disorder characterized by both visceral and somatic hyperalgesia, producing a similar effect seen with the central hypersensitivity mechanism in fibromyalgia (FM). Objectives: The aim of the current study was to compare magnitudes of visceral and thermal hypersensitivity in IBS patients and FM patients with IBS (FM + IBS) compared with healthy controls. Methods: Female patients with IBS (n = 12), FM + IBS (n = 12), and control participants (n 13) rated pain intensity to hot water immersion (45 and 47 degrees C) of the hand/foot and to phasic distension of the rectum (35, 55 mm Hg) on a Mechanical Visual Analog Scale. The data were analyzed with 3 separate 1-way analyses of variance with post hoc Tukey tests. Results: For both thermal and visceral stimuli, the control group had lower pain ratings than either the IBS or FM + IBS groups (P < 0.001). IBS patients rated rectal distension as more painful than the FM + IBS group (P = 0.005). During hot water immersion of the foot, the FM + IBS group had higher pain ratings than the IBS group (P < 0.001). During hand immersion, FM + IBS and IBS patients did not significantly differ in their pain intensity ratings (P = 0.4). Conclusions: FM + IBS patients show greater thermal hypersensitivity compared with IBS patients. However, IBS patients exhibit higher pain ratings to rectal distension compared with FM + IBS patients. This data suggests that regions of primary and secondary hyperalgesia are dependent on the primary pain complaint.