Normal Values of High-resolution Anorectal Manometry of Healthy Indians

High-resolution anorectal manometry (HRAM) measures anal sphincter function and anorectal co-ordination. This study aims to provide normal data for HRAM and evaluate the effect of gender, age, and body mass index (BMI) on anorectal functions in healthy Indian subjects.

HRAM was performed on 93 healthy volunteers using a 20-channel, water-perfused catheter. We evaluated anorectal pressures, rectal sensation, and balloon expulsion time. Measurements were recorded during rest, squeeze, and simulated defecation (push).

Median anal resting pressure (88 mmHg vs 94 mmHg, P = NS), anal squeeze pressure (165 mmHg vs 147 mmHg, P = NS) were not significantly different between males and females. Rectal pressure (70 mmHg vs 54 mmHg, P = 0.024) and anal pressure (82 mmHg vs 63 mmHg, P = 0.008) during simulated evacuation without rectal distention, were higher in males. The threshold for the first sensation was lower in females (40 mL vs 30 mL, P = 0.021) but desire to defecate (105 mL vs 90 mL, P = NS) and maximum tolerable volume (160 mL vs 140 mL, P = NS) were not significantly different in males and females. Anal residual pressure (median mmHg 83 vs 71 mmHg, P = 0.025) was higher in subjects < 40 years of age. Maximum anal squeeze pressure (185 mmHg vs 165 mmHg, P = 0.024) and maximum rectal pressure (75 mmHg vs 62 mmHg, P = 0.032) during push higher in BMI < 23 kg/m².

The present study provides normal data for the Indian population that can be used for comparison and further work. Age, gender, and BMI affect anorectal parameters in HRAM and should be considered while reporting.