Effect of aging on anorectal function.

Measurements of anorectal function were conducted on 37 elderly (66-87 years) and 48 young (19-55 years) normal subjects. Elderly subjects had decreased anal pressures compared with younger subjects, required lower rectal volumes to inhibit anal sphincter tone and had increased rectal pressures upon balloon distension. The rectal volume required to cause the desire to defecate and the maximum tolerated volume were lower in the elderly, but the corresponding rectal pressures were similar, indicating the sensations were mediated by tension, or pressure receptors. Rectal contractions were generated at similar degrees of rectal distension. A lower proportion of elderly, compared with young subjects could defecate a sphere 18 mm in diameter within 20 seconds. The degree of perineal descent was greater in the elderly female subjects compared with the young women, although there was no difference in this measurement between men. The anorectal angle was similar in young and old. The changes in anorectal function in the elderly would tend to make them more susceptible to faecal incontinence.