Effect of Aging and Gender on Internal Anal Sphincter Thickness

Abstract

The prevalence of fecal incontinence (FI) in the general population increases with age in male and female. The internal anal sphincter (IAS) plays a key role in maintaining continence, providing a large part of the maximum resting pressure (MRP). Increasing age is associated with a weakening of the MRP. The IAS thickness was measured using an ultrasound scanner with a 10 MHz rotating endoprobe in 774 subjects (382 female and 392 male). There was a positive correlation between the thickness of IAS and age in both sexes. In female, the thickness of IAS did not change from 20’s (1.89±0.41) to 40’s (2.06±0.52), but increased after 50’s (2.32±0.47) with age. In male, after 50’s (2.14±0.54) was significantly thicker than to 40’s (1.86±0.54). The thickness of IAS was thicker in female than in male (2.30±0.60 and 2.05±0.53, p < 0.001). It is known that the MRP decreases with age, therefore an increase of IAS thickness in the elderly may be an attempt at compensation, which ultimately fails because of a loss of tone.