Effect of continuous rectal distention on anal resting pressure.
OBJECTIVE
Intermittent distention of the rectum induces internal anal sphincter relaxation, but whether continuous rectal distention might affect the resting pressure of the anal canal and the frequency of internal anal sphincter relaxations has not yet been investigated. The aim of this study was to record anal pressure under resting conditions and at two levels of continuous rectal distention.


METHODS
Anal pressure was recorded by means of water-perfused catheters under resting conditions and at two levels of rectal distention controlled by an electronic barostat in eight healthy subjects.


RESULTS
Continuous rectal distention did not significantly change mean anal resting pressure, but it did significantly decrease the amplitude of ultraslow waves (from 29 +/- 9 mmHg under resting conditions to 23 +/- 6 and 21 +/- 3 mmHg during lesser and greater rectal distention; P = 0.017 and P = 0.012, respectively) and increase the frequency of internal anal sphincter relaxations (from 1.3 +/- 1.3/hour under resting conditions to 8.8 +/- 4.3/hour and 11.0 +/- 4.8/hour during lesser and greater distention; P = 0.012 in both comparisons).


CONCLUSIONS
The resting pressure of the anal canal is maintained during continuous rectal distention. The decreased amplitude of ultraslow waves and increased frequency of the internal anal sphincter relaxations induced by rectal distention reveal a complex functional relationship between the rectum and the anal canal.
Mularczyk
A
A
Cattedra di Gastroenterologia, Istituto di Scienze Mediche dell'Università degli Studi di Milano, IRCCS Ospedale Maggiore di Milano, Milan, Italy.
Bianchi
P A
PA
Basilisco
G
G
D000328:Adult; D001003:Anal Canal / Q000502:physiology*; D005260:Female; D005769:Gastrointestinal Motility; D006801:Humans; D008297:Male; D011312:Pressure; D012007:Rectum / Q000502:physiology*