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).
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.
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.
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).
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.