An experimental pain model based on electric stimulations of the colon mucosa

Background: Pain intensity and distribution related to diseases of the gut are important diagnostic indicators in gastroenterology. Experimental pain models provide a unique possibility for standardized activation of the noci ceptive system, but only few human models exist. Methods: An experimental p ain model based on electric stimuli in the human colon was developed and ap plied. Eleven patients who were referred for surveillance colonoscopy due t o earlier polyps in the colon were included. None had any abdominal pain co mplaints. The following areas were stimulated with 'single', 'repeated', or 'continuous' electric current: the cecum, the hepatic and splenic flexures , and the rectosigmoid junction. Results: All subjects felt deep, diffuse p ain during the stimulation, with referral to localized somatic structures. The pain detection thresholds after repeated stimuli were similar in the fo ur areas. The threshold for single stimulation was higher than the threshol d for repeated stimulation. Most reported pain in the lower and left site o f the abdominal wall during stimuli at the splenic flexure and rectosigmoid junction. Stimuli at the right colon, however, resulted mostly in pain at the contralateral site of the abdomen. Conclusions: The presented model was robust and suitable for eliciting pain in different regions of the large i ntestine. The importance of temporal summation in visceral pain was shown. Mapping of the referred pain areas mimics clinical observations and has ont ogenetic and anatomic consistency. The model may therefore improve the eval uation of pain in patients with diseases of the colon.