Pain Produced by Electric Stimulation of the Rectum in Patients with Irritable Bowel Syndrome: Further Evidence of Visceral Hyperalgesia

Background: Visceral hyperalgesia is most likely a phenomenon of substantial clinical importance and may also play a role in the pathophysiology of the irritable bowel syndrome (IBS). We investigated the manifestation of visceral hyperalgesia in IBS patients by nociceptive electric stimulation of the rectosigmoid junction and rectum. Methods: Twelve IBS patients fulfilling the Rome criteria and 9 healthy controls were studied. Visceral single and repeated electric burst stimuli were applied with a bipolar electric stimulator inserted through the sigmoidoscope. The sensation (ST) and pain detection (PDT) thresholds were determined in response to single and repeated stimuli at the rectosigmoid junction, and PDT to repeated stimuli at four different positions in the rectum. Cutaneous single and repeated electric stimuli were applied to the lateral aspect of the foot, determining ST and PDT. Results: Cutaneous stimulation showed no significant differences for ST and PDT between patients and controls. The rectosigmoid junction showed significantly lower ST for single stimuli (P < 0.01) and a significantly lower PDT for single and for repeated stimuli (P < 0.05 and P < 0.02) in IBS patients. In the rectum the IBS patients had a significantly lower PDT than controls (P < 0.001). Conclusions: For cutaneous electric stimulation no differences in the pain thresholds between the two groups were found, showing that there is no generalized hyperalgesia in IBS patients. The IBS patients had a specific decrease of the pain thresholds in the rectum and rectosigmoid junction, indicating visceral hyperalgesia. These results point to central visceral hyperexcitability as an important factor in the pathophysiology of IBS.