Anal sensation and the continence mechanism

Thermal sensation is thought to be important in sensory discrimination between different substances. The aim of this study was to determine the thermal sensitivity in the anal canal in continent patients with hemorrhoids (N = 20), a group that has been reported to have a sensory deficit, and to compare the results with control subjects (N = 40) and patients with idiopathic fecal incontinence (IFI) (N = 22). Anal manometry was performed and sensation to mucosal electrostimulation and temperature change in the lower, middle, and upper zones of the anal canal assessed. Thermal sensation was impaired in the hemorrhoid group as compared with controls, but not to the same degree as in IFI (e.g., median thermal sensitivity in mid anal canal, control 0.9 degrees C, hemorrhoid 1.2 degrees C, IFI 2.0 degrees C, P less than .05 and less than .001, respectively). The correlation between the two tests of sensation was 0.54 (P less than .001) and the reproducibility of thermal sensory thresholds was 0.82 (P less than .001). In conclusion, patients with hemorrhoids have a mild anal sensory deficit, but continence in this group is likely to be augmented by other factors.