Gender differences in the longitudinal pressure profile of the anal canal related to anatomical structure as demonstrated on three-dimensional anal endosonography
Ab. Williams et al., Gender differences in the longitudinal pressure profile of the anal canal related to anatomical structure as demonstrated on three-dimensional anal endosonography, BR J SURG, 87(12), 2000, pp. 1674-1679
Background: Anal canal squeeze pressure is assumed to be due to external sp
hincter contraction, but the contribution of other muscles has not been exp
lored.
Methods: Ten male and ten nulliparous female asymptomatic subjects had thre
e-dimensional anal endosonography and manometry. Incremental squeeze pressu
res at 0.5-cm intervals, expressed as a percentage of the maximum pressure
recorded anywhere in the canal, were related to the following anatomical le
vels: puborectalis, overlap between external anal sphincter (EAS) and pubor
ectalis, external and internal anal sphincters, and external anal sphincter
only. Levels were determined by coronal and sagittal endosonographic recon
structions.
Results: Puborectalis was the same length in men and women (median 23.9 ver
sus 27.1 mm) but represented a greater proportion of the anal canal in wome
n (45 versus 61 per cent; P = 0.02). At the level of puborectalis alone, th
e pressure generated as a proportion of maximum anal canal pressure was 71
(range 32-100) per cent in men and 62 (range 32-100) per cent in women. At
the level of the EAS alone, the pressure was 60 (4-98) per cent in men and
82 (41-100) per cent in women; where the external sphincter was overlapped
by puborectalis, the pressure was 98 (60-100) per cent in men and 75 (47-10
0) per cent in women.
Conclusion: Maximal anal canal squeeze pressure is found where the puborect
alis overlaps the EAS. This segment represents a significant proportion of
anal canal length in women.