[Sensitivity of the anal canal: study techniques and results in normal subjects]

To describe a technique for the study of the anal canal sensitivity to electric and thermal stimulation, and to investigate it prospectively in normal subjects.

Mucosal electrosensitivity and thermal sensation of the anal canal is correlated with motor parameters: perineometry, manometry and electrophysiology.

41 control subjects (20M & 21F) with normal anorectal anatomophysiology.

In the middle anal canal minimum electrosensibility thresholds were present, and they were similar to the thermal profile. A significant impairment in electrosensitivity was observed as a function of age, but no differences between the sexes were found. Lower thresholds were obtained than cold temperatures (p < 0.001). Both tests of sensitivity correlated with pudendal motor parameters. The maximal thermal difference in the anal canal was 0.28 degree C, while the minimal detectable temperature change was 0.46 +/- 0.1 degrees C.

The sensitivity of the anal canal is greatest in the zone of the anal valves and better in response to hot than cold stimulus. As the minimum detectable temperature change has been greater than the difference of temperature between the low and high anal canal, we suggest that discrimination is not possible on the basis of thermal differences.