Determinant of anal resting pressure gradient in association with continence function.

Background/aims: Gradient of resting pressure across the anal canal, which is known to have a role in continence mechanism, has 2 components of determination; pressure and length factor of the anal canal. This study evaluates which factor between them plays more significant role for the determination of the gradient in association with continence function.

Methods: Anal manometric measurements of 69 patients with fecal incontinence and 60 controls were retrospectively reviewed. In addition to resting pressure gradient, typical manometric parameters such as maximum resting pressure, basal resting pressure, length of the anal canal, length of high pressure zone and relative position of highest pressure, which were measured with rapid pull-through technique were all contrasted.

Results: Demographics of the 2 groups were similar. Maximum resting pressures of patients with incontinence and controls were 59.1 ± 28.3, 74.6 ± 24.0 mmHg (P = 0.001), respectively. Basal resting pressures were 5.7 ± 6.4 and 7.3 ± 3.9 mmHg (P = 0.097), lengths of the anal canal were 35.8 ± 9.1 and 38.1 ± 8.3 mm (P = 0.133), lengths of high pressure zone were 21.2 ± 6.7 and 23.3 ± 6.5 mm (P = 0.091), relative positions of highest pressure were 69.2 ± 10.6 and 70.1% ± 14.9% (P = 0.717) and resting pressure gradients were 2.28 ± 1.08 and 2.74 ± 1.14 mmHg/mm (P = 0.019), respectively. Difference was significant in maximum resting pressure and resting pressure gradient, but not in length factors such as full length of the anal canal, length of high pressure zone and relative position of highest pressure.

Conclusions: Proximal location of high pressure zone in incontinent patients is not definite and resting pressure gradient of the anal canal depends more on pressure factor than length factor in association with continence function.