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| 번호 | 제목 | 등록일 | 조회수 |
|---|---|---|---|
| 70 | Combined Radiologic and Manometric Study of Rectal Filling Sensation [2002년 8월 DCR] | 2011-11-17 | 3964 |
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Paul Broens, M.D., Dirk Vanbeckevoort, M.D., Erwin Bellon, M.Sc.,Freddy Penninckx, M.D., Ph.D.
From the Departments of *Abdominal Surgery and †Radiology, University Clinic Gasthuisberg, and Medical Image Computing (Radiology and ESAT/PSI), Catholic University of Leuven, Leuven, Belgium
PURPOSE: Sensation is an essential aspect of fecal continence. We aimed to correlate manovolumetric and radiologic changes at successive levels of rectal filling sensation.
METHODS: Combined anorectal manometry and proctography were performed in nine volunteers. Images, volumes, and pressures were analyzed at the start of the test, at 20 seconds before first
sensation, and at first, constant, urge, and maximum tolerable sensation. RESULTS: Consecutive levels of rectal filling sensation were associated with progressive opening and dilation of the upper anal canal (up to 44 mm) and sliding down of the rectal contents (14 mm), which had already started before the first sensation. This coincided initially with a pressure decrease in the proximal anal canal (from 94 to 42 mmHg). With constant sensation and particularly with urge sensation, rectal pressure increase appeared to be responsible for further proximal anal dilation. This was accompanied by a significant increase of proximal anal pressure (up to 133 mmHg) and sharpening of the angle between the anal axis and the horizontal reference line.
CONCLUSION: The proximal anal canal or its surrounding structures play an important role in the
desire-to-defecate sensation. They can be activated by a progressive buildup of rectal reservoir pressure in the presence of a competent distal anal sphincter barrier. Normal fecal continence and defecation need a compliant reservoir, competent sphincter function,
and timely sensation. One might distinguish between rectal filling and anal sampling sensation. Anal sampling permits discrimination between gas, liquid stool, and solid stool. Sampling has been postulated to be related to relaxation of the internal sphincter with pressure reduction in the proximal anal canal in response to rectal filling or contraction. This would allow rectal contents to make contact with the sensitive mucosal lining in the upper anal canal. Rectal filling sensation, particularly urge or the imperative desire to defecate, is also essential for normal fecal continence and defecation to occur. Rectal filling can be simulated most simply by the incremental distention of a rectal balloon while the volumes needed to provoke a sensation are recorded from the first sensation until the maximum tolerable level of sensation. For more detailed studies, rectal manovolumetric tests can be performed to simultaneously assess rectal capacity and compliance, as well as pressure and volume thresholds at individual sensation levels that occur during rapid and
incremental or slow and progressive rectal distention with air or water. Pressure can be recorded simultaneously in the upper anal canal (mainly the internal sphincter) and the lower anal canal (mainly the external anal sphincter) to evaluate inhibitory and contractile sphincter reflexes. Proctography with or without a balloon has been introduced to study the anorectal angle and the level of
the pelvic floor. The much more popular technique of defecography with barium paste with the consistency of normal stool is performed to visualize the dynamic events during straining and defecation. To the best of our knowledge, the relation between rectal filling sensation and concomitant radiologic and manometric changes in the anorectum has never been investigated. The aim of this study, therefore, was to correlate manometric and morphologic changes that accompany successive sensation levels, particularly urge sensation, such as can be provoked by progressive rectal filling.
DISCUSSION
Rectal filling sensations persist and can be provoked after complete rectal excision and construction
of a coloanal anastomosis, a colon pouch-anal anastomosis, or an ileal pouch-anal anastomosis. Thus, the receptors involved must lie outside the bowel, and it has been suggested that the pelvic
musculature may be involved. The present study did not aim to investigate the nature or location of these receptors; however, it illustrates that the upper part of the anal canal or its surrounding tissues are involved in what is called rectal filling sensation. The proximal anal pressure decrease that we observed even before FS was reached can be explained
by reflex internal sphincter relaxation, as occurs in the frequently tested rectoanal inhibitory reflex. Upper anal sphincter relaxation was also shown to be involved in the sampling reflex. This allows descent of the rectal contents. Thus, simple contact of the latter with the mucosal lining at the anorectal junction does not appear to be sufficient to induce a filling sensation. Further entry of the rectal contents in the upper anal canal and, in particular, building up of tension (pressure) at that level appear to be important events accompanying the more pronounced constant feeling of rectal filling and urge to defecate.
CS and US were characterized by several events that occurred simultaneously at the rectal and upper
anal levels. Although the rectal wall “adapts” to progressive filling initially, it becomes more and more resistant to stretch during further distention, starting from FS and becoming most pronounced at US. This is illustrated by the fact that the local pressure detected by the rectal microballoon increased more steeply than the pressure in the rectal balloon, the difference being significant from CS. This resistance to further stretch will force the rectal contents into the anal canal. We have documented that rectal intraballoon pressure was more related to the successive levels of filling sensation than volume or weight. Thus, a not-too-compliant reservoir (rectum or neorectum) is required for the induction of filling sensations. Indeed, in patients with megarectum or rectal inertia, filling sensations can only be provoked late (with a shift to the right on the pressure/volume diagram) or not at all. CS and US were characterized not only by the rectal pressure increase pushing its contents (balloon)
down into the upper and mid anal canal, resulting in the anorectal junction becoming funnel shaped, but also by pressure and wall tension building up at that level, while the distal anal third remained perfectly closed. The greater proximal anal pressure increase can be explained by compression from the descending rectal contents and/or by resistance to distention of the surrounding tissues. Puborectalis muscle contraction or resistance to progressive stretch appears to be involved, at least in part. The anorectal angle, measured through the midrectal axis, decreased from start to US, as did the angle between the anal axis and the horizontal reference line. |
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