Detection of colon distension in colonostomy patients

Inborn and learned ability to detect mild, nonpainful distension of the sygmoid colon was examined in 22 patients who underwent colonostomy one year or more before the investigation. The colon was distended by a balloon inserted 10 cm below the orifice of the artificial anus. Each subject participated in three sessions on three consecutive weeks with several experimental tasks in each session. During each task, the patient received the colon stimulus (the "signal") 25 times randomly paired with masking auditory or annular skin stimuli (around the stoma or 15 cm medially to it). The masking (warning) stimuli were administered in series of 50, representing the "noise," according to signal-detection paradigms. The subjects had to indicate after each administration of the warning noise stimulus whether or not they thought the colon stimulus had been presented. In all three sessions, learning tasks were included using reinforcement of successful detection trials. Seven subjects out of 22 were considered good perceivers, 9 persons were considered medium perceivers, and the remaining 6 subjects were considered poor perceivers. According to the data of the first two groups, it can be hypothesized that most patients have some inherent sensitivity of colon distension, and that learning improves this initial ability. However, the role of skin, peritoneal, or interstitial receptors in colon distension detection cannot be excluded.