The composition of anal basal pressure

Abstract

The maximal anal basal pressure (MABP) was measured with probes of 0.3, 1, 2 and 3 cm diameter in 21 subjects, 60 years old, without anal pathology. The components of MABP were analyzed by inducing a maximal internal sphincter (IS) relaxation, taking pressure measurements in the conscious state and during narcosis with curarization. In seven cases pressure measurements were done on isolated anorectum after abdominoperineal rectum amputation. MABP increases with probe diameter before as well as during anaesthesia with curarization. The contribution of the striated sphincter tonic activity is constant within the range of probe diameters used. At rest, i.e. when the 0.3 cm diameter pressure recording probe is used, 30% of MABP is made up by striated sphincter tonic activity, 45% of it is due to nerve induced IS activity, 10% to purely myogenic IS activity and 15% can be attributed to the expansion of the haemorrhoidal plexuses. Although MABP is mainly based on active forces generated by the smooth and striated sphincter apparatus, the presence of the anal cushions is essential for perfect anal continence, as they have to fill the gap within the IS ring to hermetically close the anal canal. The global IS activity, contributing 50-60% of MABP at rest, can completely be inhibited by a maximal rectoanal inhibitory reflex. Stretching of passive elements starts at 1 cm anal distension, but steeply increases thereafter, accounting for 65% of the MABP at 3 cm anal distension. It is deduced that optimal stool diameter is about 2 cm.

The Surgical Management of Haemorrhoids – A Review

“…The ability of the anal cushions to alter their volume through their vascular component allows for both the preservation of continence and the passage of stool. Vascular filling is thought to contribute between 15 and 20% of resting anal pressure [8]. …”

Measurement of Anal Cross-Sectional Area and Pressure during Anal Distension in Healthy Volunteers

“…Most of these were developed to detect pressure and changes in pressure. Measurement of CA has only been vaguely studied [9,10] and not during dynamic distension as in this study.…”

“…Mea surement of pressure-CA relations in the anal-sphincter region may enhance our knowledge of the continence and defecation mechanism in physiological and diseased states. Until now anal wall properties during distension have only been vaguely studied using rigid plastic probes [9,10], partly be cause no method existed to measure it [15].…”

Anal vector volume analysis: an effective tool in the management of pelvic floor disorders

“…The most commonly used parameters in conventional anal manometry are the resting anal pressure and the maximum anal pressure following a voluntary squeeze effort [7][8][9]. In conventional anal manometry, where micro-balloons are used, these pressures comprise the mathematic circumferential mean of all the pressures of the anal canal surface touching the balloon.…”