Normative values in anorectal manometry using microtip technology: a cohort study in 172 subjects.

PURPOSE: The aims of this study were to obtain normative values in resting/squeeze pressure and surface electromyography (s-EMG) in anorectal manometry using microtip technology and to determine the relationship between objective measurable values, gender and age in a cohort with no anorectal disorders.
METHODS: One hundred seventy-two white central European subjects (106 males/66 females) were recruited prior to left colonic or upper rectal surgery and studied by anorectal rapid pull-through manometry with a microtip transducer system and endoanal s-EMG using a bipolar plug electrode. s-EMG patterns were determined as plateau, peak and decrease by a blinded co-investigator. Objective measurable sphincter pressures and s-EMG values were correlated with gender, age and s-EMG patterns.
RESULTS: Squeeze pressure, voluntary pressure as well as s-EMG amplitude and its area under the curve were significantly lower in women compared to men (p < 0.001 each), whereas resting pressure showed no gender differences. s-EMG patterns were strongly influenced by gender. Male patients showed significantly more plateau pattern whereas peak pattern was significantly more often in women. In both genders, the peak pattern was associated with significant higher squeeze pressures. In all measurements, we found considerable inter-individual variations being higher in elder patients. There was no manometric parameter correlating with age.
CONCLUSIONS: Gender is the strongest factor influencing objective measurable manometric data for healthy men and women. There are significant gender differences concerning squeeze patterns. All manometric values should be interpreted in the context of gender and of methodology used. Large prospective cohort studies matched for gender are necessary to clarify the effect of ageing on anal sphincter strength.