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 substantia l clinical importance and may also play a role in the pathophysiology of th e irritable bowel syndrome (IBS). We investigated the manifestation of visc eral hyperalgesia in IBS patients by nociceptive electric stimulation of th e 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 stimu lator inserted through the sigmoidoscope. The sensation (ST) and pain detec tion (PDT) thresholds were determined in response to single and repeated st imuli at the rectosigmoid junction, and PDT to repeated stimuli at four dif ferent positions in the rectum. Cutaneous single and repeated electric stim uli were applied to the lateral aspect of the foot, determining ST and PDT. Results: Cutaneous stimulation showed no significant differences for ST an d PDT between patients and controls. The rectosigmoid junction showed signi ficantly lower ST for single stimuli (P < 0.01) and a significantly lower P DT for single and for repeated stimuli (P < 0.05 and P < 0.02) in IBS patie nts. In the rectum the IBS patients had a significantly lower PDT than cont rols (P < 0.001). Conclusions: For cutaneous electric stimulation no differ ences in the pain thresholds between the two groups were found, showing tha t there is no generalized hyperalgesia in IBS patients. The IBS patients ha d 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 o f IBS.