Pain hypersensitivity in patients with functional gastrointestinal disorders - A gastrointestinal-specific defect or a general systemic condition?

Visceral hypersensitivity was shown in patients with functional gastrointestinal disorders (FGID). The mechanisms underlying this sensory dysfunction remain undetermined. The; initial hypothesis of a generalized reduction in pain tolerance was rejected by further studies that suggested a normal tolerance to somatic stimuli and led to the generally accepted assumption that pain intolerance is specific and exclusive for visceral stimuli in these patients. We wanted to revisit this theory by examining whether patients with FGID reported perception and tolerance to somatic pain differently from normal subjects and whether the response to somatic pain stimulus was correlated to gastrointestinal symptoms or psychological status or distress. Thirty-three patients with FGID (Rome II criteria)(F/M: 26/7; mean age 48 +/- 9.9) and 33 normal controls (F/M: 24/9; mean age 44.1 +/- 6.8) were asked to immerse their nondominant hand into 4 degreesC water for as long as possible (maximum 120 sec). Time before appearance of: (1) discomfort, (2) pain, and (3) withdrawing of the hand were noted. The intensity of pain was rated on a visual analog scale from 0 to 100. Self-report questionnaires were used to assess the severity of gastrointestinal symptoms (St-Luc GI index) and the psychological distress (SCL-90) in the patient group. Data are expressed in seconds as mean +/- sEM. Discomfort sensory thresholds were similar in controls and FGID patients (28 +/- 3 and 24 +/- 2, respectively; NS) whereas pain and withdrawing were significantly lower in FGID (41 +/- 3 and 76 +/- 6 sec) than in controls (62 +/- 6 and 102 +/- 4; P < 0.05). Pain intensity was similar in both groups (64 <plus/minus> 4 vs 67 +/- 3; NS). Female patients showed lower sensory thresholds than male patients and control females (pain thresholds: 39.8 +/- 3.4 vs 67.8 +/- 16.7 and vs 56.8 +/- 8.7; P < 0.05). Sensory thresholds were not different in subgroups of patients with FGID (irritable bowel syndrome and functional dyspepsia). No correlation was shown between sensory thresholds and gastrointestinal index or SCL 90-test. In conclusion, FGID patients showed a threshold to painful somatic stimulus that was lower than in normal subjects. These findings suggest that patients with FGID may have hyperalgesia and low pain tolerance: that is not limited to the viscera, but that is part of a systemic general condition.