Effects of age and sex on anorectal manometry.

We studied rectal and anal function in 18 healthy elderly and 18 healthy young adults using intraluminal pressure transducers and a rectal balloon. Both age groups consisted of nine females and nine males. Age did not affect anal length, highest anal resting tone, anal pullthrough pressures obtained during rest and voluntary squeeze, threshold of the rectosphincteric reflex (RSR), amplitude of RSR with 60 ml rectal distension, threshold of sensation, critical volume, and rectal wall elasticity. Sex did not affect anal length, threshold of RSR, amplitude of RSR with 60 ml rectal distension, the critical volume and rectal wall elasticity. But the highest anal resting tone, anal pullthrough pressures obtained during rest and voluntary squeeze, and threshold of rectal sensation were significantly higher in the males than in the females. While aging did not affect anal and rectal function, sex did. Males achieved higher anal canal pressures. Therefore, statistical comparison between different groups of subjects is valid only if the groups are matched for sex.