Physiological variation in rectal compliance.

The volume (V) of air inflated in a latex balloon placed in the rectum and the corresponding pressures (P) were measured in 48 subjects (24 men and 24 women) at three points: (1) earliest defaecation urge; (2) constant defaecation urge; and (3) maximum tolerable volume (MTV). The rectal pressures in all three cases were higher in men than in women. Woman aged over 60 years had higher rectal compliance (delta V/delta P) than men in the same age group, while no difference was found between men and women below the age of 60 years. Day-to-day variation of the measurements was tested in ten subjects. Reproducibility was good only for MTV (95 per cent confidence interval 57-183 per cent). Reproducibility of rectal compliance decreased with increasing values for this parameter. No such trend was found for the other parameters. In conclusion, MTV is a reproducible parameter and suitable for clinical use in evaluation of patients with faecal incontinence or constipation.