Background and Objectives : Diseases of the distal gastrointestinal tract are becoming more common among
Thai people especially in the elderly. Manometry is a new and useful technique in the diagnosis and management of anorectal disorders. This cross-sectional study aimed to measure anorectal manometric parameters in normal Thai subjects.
Material and Method : Thirty healthy Thai subjects (17 males and 13 females) were studied. They completed a questionnaire assessing their bowel function. A water-perfused manometric system with non-pull-through technique was used to monitor pressure in the rectum and anus. All subjects were asked to squeeze the anal sphincters, bear down, then blow up a party balloon. Rectal sensation and recto-anal inhibitory reflex were
also assessed by intermittent phasic balloon distention. Simulated defecation or balloon expulsion test was also performed.
Result : The study revealed the following anorectal manometric parameters. The mean with standard deviation of the resting, squeezed, and sustained squeezed pressures were 55.4 + 15.3, 170.3 + 81.7 and 109.3 + 54.4 mm Hg respectively. Men had a longer anal sphincter (p = 0.01) and higher squeezed, and sustained squeezed pressures (p < 0.001) compared to women, while their resting sphincter pressures were similar. Threshold volumes for rectal sensation and desire to defecate were not different among male and female subjects, but the threshold for urgency to defecate was higher in men. The study yielded normal anorectal manometric parameters in Thai subjects. Some parameters vary with gender. It is difficult to compare these normal ranges in Thai subjects to those in Caucasians, as the number of subjects is rather small and the details of instruments and techniques always vary from lab to lab. The manometric findings in these Thai subjects create more understanding in anorectal physiology and can be used as a guideline for the investigation of anorectal function in a symptomatic Thai population in a motility clinic.

Keywords : Anorectal manometry, Anal sphincter, Gender