Anal canal pressure profile: a reappraisal as determined by rapid pullthrough technique

Previous station pull through techniques of anal canal pressure measurement have not truly represented the differences among individuals and between sexes in the length and pressure profile of the anal canal. Furthermore, the techniques commonly used in anal canal pressure determination have not been adequately compared or standardised. Therefore, a mechanised rapid pull through technique using an 8-lumen, 4-quadrant, continuously perfused catheter was evaluated and used to define the anal canal pressure profile. For measurement of the resting anal canal pressures, this technique was compared with the more usual station pull through technique in 12 subjects. There were no differences in resting pressure recorded by either technique with infusion rates ranging from 0.5 to 1.2 cc/min/orifice and over a range of catheter withdrawal rates of 0.19 to 0.48 cm/sec. Twenty two subjects (12 men/10 women) had their anal canal pressure profiles assessed using the rapid pull through technique. Anal canal length representing the mean of four axes differed between the sexes (p less than 0.005) and the difference was largely accounted for by a decrease in length of the anterior axis in women. A standardisation technique was used to account for between subject variation and for a more accurate between sex comparison of the pressure profiles. Significant differences in radial symmetry were found between the sexes. In the anterior axis the pressure was higher distally in women, while in the anterior and lateral axes the pressure was higher proximally in men. Anteriorly in women the highest pressures were exerted over a much shorter canal length than in men. We conclude that the usual station pull through technique can give reliable resting pressure measurements in the anal canal. The rapid pull through technique described herein, however, used a flexible catheter system which follows the normal anal canal and rectal contours, allows a more appropriate assessment of the anal sphincter profile, and provides findings that are consistent with the known local anatomy.