A study of the physiological variation in anal manometry.

The physiological variation in anal manometry using a perfused catheter with radiating sideholes was studied in 78 healthy volunteers. The maximum intraindividual variation in the length of the anal high pressure zone, resting pressure and squeeze pressure was 10 mm, 26 mmHg and 68 mmHg respectively. The median 95 per cent confidence interval for length of the pressure zone was 4 mm; for resting pressure it was 15 mmHg and for squeeze pressure it was 48 mmHg. Day-to-day variation did not exceed the intraindividual variation. Constant recording with the catheter fixed in the high pressure zone revealed slow waves and ultraslow waves with amplitudes of 6-24 mmHg which could account for most of the intraindividual variation. No sex difference was found in the length of the high pressure zone whereas resting pressure and squeeze pressure were higher in men than in women. Although a tendency towards a decrease in the length of the high pressure zone, resting pressure and squeeze pressure was observed with increasing age, no significant age-related difference could be demonstrated.