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.

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