Ambulatory manometric recording of anorectal activity

Ambulatory anorectal manometry is usually analyzed by computer analysis only. An in-depth analysis with visual assessment of the recordings combined with computer analysis is presented.

Recordings of 20 to 24 hours in length were performed on ten healthy subjects. Spontaneous anal canal relaxations were analyzed and related to changes in rectal pressure and any reported rectal sensation. Pressure variations in the anorectum, including the rectal motor complex, were studied.

In the awake subject the frequency of anal canal relaxations was 14.5 to 18.7/hour, and the frequency was 4.3/hour while asleep. They can be divided into two different subtypes. The amplitude of the pressure fall was 26 to 29 mm Hg, but diminished during sleep to 19 mm Hg. The duration of each relaxation was 16 to 19 seconds. Passage of flatus and the sensation of flatus in the rectum occurs 1.5 and 1.2 times per hour, respectively, usually with simultaneous anal canal relaxation. The frequency of rectal motor complexes in the midrectum was 0.4/hour and in the lower rectum was 0.7/hour; the duration was 10.3 and 5.8 minutes, respectively, with no nocturnal variation. The complexes could not be related to anorectal events.

The study provides supplementary knowledge of anorectal physiology, particularly of anal canal relaxation, and proposes a more detailed method for evaluation of data obtained by ambulatory anorectal manometry.