肛肠动力文献 (6)
Manometric asymmetry of the anal sphincter: anatomic evidence and clinical application
XIAO Yuan-hong, LIU Gui-lin
XIAO Yuan-hong Department of Pediatric Surgery, PLA General Hospital, Beijing 100853, China; LIU Gui-lin Department of Pediatric Surgery, PLA General Hospital, Beijing 100853, China
Correspondence to: XIAO Yuan-hong Department of Pediatric Surgery, PLA General Hospital, Beijing 100853, China (Tel:86-10-66937123
Email:hcj5306@https://www.360docs.net/doc/9213200513.html, )
Keywords:anus·manometry·anal sphincter·pressure·manometric asymmetry gradient·anatomy
Abstract:
Background Manometric pressure asymmetry of the anal sphincter exists in the anal canal. There are reports about the anatomy of the anal sphincter, but the relationship between the configuration and the pressure asymmetry of the anal sphincter is not clear. This study is to investigate the anatomic evidence and clinical application of anal sphincter pressure asymmetry.
Methods PC polygram HR at the state of relaxing and squeezing was used in 27 normal children and 12 abnormal ones with fecal incontinence.
Results In normal children, longitudinal pressure gradients existed at eight channels in the anal canal, and the maximal pressure 1 cm from the anal verge. Longitudinal pressure asymmetry changes of eight channels also existed in the anal canal, from 3 cm to 2 cm to 1 cm from the anal verge. The high pressure distribution changed from the posterior to the anterior anal canal. Anteriorly, 1 cm from the anal verge, the maximal pressure was formed in the anal canal. However, neither longitudinal pressure gradients nor longitudinal pressure asymmetry changes were seen in patients with fecal incontinence.
Conclusion The configuration and function of the striated muscle complex possibly contribute to the formation of the pressure asymmetry of the anal sphincter, which is essential to anal control.
CMJ 2005;118(3):210-214 ·LogIn/LogOut
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As an important method for the functional detection of the anal sphincter, anorectal manometry has been widely used in clinical practice. From 3 cm to 2 cm to 1 cm of the anal verge, there are gradually increasing pressure gradients in the anal canal, including the mean relaxing pressure and the mean squeezing pressure. One cm from the anal verge there is the maximal pressure. Also gradually decreasing pressure asymmetry gradients exist in the anal canal, including the mean relaxing pressure asymmetry and the mean squeezing pressure asymmetry, and 1 cm from the anal verge there is the minimal pressure asymmetry (over zero).［1］It is 1 cm from the anal verge where the maximal pressure and minimal pressure asymmetry are formed this circumference is called the center of the striated muscle complex. When approaching to this center, the pressure is increased and pressure asymmetry decreased gradually.［1］If it is the absolute equality of the pressures at different positions of the same circumference in the anal canal, the pressure asymmetry should be zero. However, we discovered that even if at the center of the striated muscle complex, the pressure asymmetry was over zero. The mean relaxing pressure asymmetry was (26.61±17.11)%, and the mean maximal squeezing pressure asymmetry was (24.33±14.31)%.［1］That is to say the pressure distribution is asymmetric. We have tried to detect the relationship between the pressure asymmetry and the anatomy to the anal sphincter and assess the clinical use of the asymmetry.
METHODS
Subjects
Between October 1998 and May 1999, 27 normal children (4- to 14-year-old, without disorders of the anorectum and the nerverus system, 14 male children and 13 female, mean weight 29 kg), and 12 patients with fecal incontinence (6- to 19-year-old，10 male chlidren and 2 female, mean weight 31.7 kg) participated in the study with the approval of their parents. In the group of patients included 3 patients suffered from anal atresia and was operated on with anorectal plasty via the abdomen-peritoneum approach, 5 patients suffered
from the anal atresia and operated by the graciloplasty as an alternative to the anal sphincter. One patient had a cloaca malformation and another suffered anal atresia and fistula between the rectum and urethra, and was operated on with posterior sagittal anorectoplasty. One patient with congenital Hirschsprung's disease developed night anal incontinence postoperatively. One patient had a severe trauma in a traffic accident and was operated on with posterior sagittal anorectoplasty followed by graciloplasty as an alternative to the anal sphincter.
Manometric machine and detective methods
Manometric procedures were performed in the left lateral decubitus position. No bowel preparation was needed. Manometry was performed using an
eight-lumen polyvinyl chloride catheter (CTD Company, Sweden) connected to a pneumohydraulic capillary perfusion system and perfused with sterile degassed water at 2 ml/min for each channel using a perfusion pressure of 300 mmHg. Perfusion holes were located 5 cm from the catheter tip and the eight 1 mm-diameter side-holes spaced at 45-degree intervals around the circumference. Channel 1 was identified by a longitudinal blue line along the catheter. Each channel had its own preamplifier and the signals from them were received by the PC polygram, which was a multipurpose data acquisition device. The PC polygram measured the data, converted them to digital information, and then transferred it to an IBM-compatible computer via a fiberoptic interface, which also served as an electrical isolation between the child and the computer. The data were displayed on the computer screen during the recording and were stored on the disk for later examination and analysis. Before a manometric procedure, the catheter-perfusion system was calibrated to 50 mmHg using a meter rule and then calibrated to the individual with 0 mmHg at the level of the anal verge. The catheter was inserted into the anal canal to a distance of 6 cm from the anal verge so that channel 1 corresponded to the dorsal as viewed in the lithotomy position and left until a steady manometric trace was obtained. The data were collected using a station pull-through technique. Once the child was comfortable and the manometric trace was stabilized, recording was commenced at 6 cm from the anal verge with a 0.5 cm withdrawal , and radial orientation was maintained constantly. At any cross-section, all of the children were asked to relax and squeeze their anus without the maneuver of their leg muscles and gluteus. The duration of the two actions was 20 seconds each and the interval between them was 20-30 seconds.
Parameters
When relaxing and squeezing, the longitudinal pressures of eight channels were meansured at the circumferences of 6，5，4，3，2，1 cm from the anal verge. The radial pressures of the eight channels were determined at the circumferences of 3, 2, 1 cm from the anal verge (mmHg).
Statistical analysis
Every sample was tested by the normality test, and Wilcoxon's rank-sum test was used for the differences among multiple samples. Chinese high intellectualized statistical software (CHISS) was used. Mean values were shown when more samples presented with normal distribution, while median values were displayed when more samples presented with asymmetric distribution.
RESULTS
Relaxing
Normal children
For every channel ［i.e. anterior (A), left-anterior (LA), left (L), left-posterior (LP), posterior (P), right-posterior (RP), right (R), right-anterior (RA)］, longitudinal pressure gradients existed from the circumferences 3 cm to 2 cm to 1 cm of the anal verge （P<0.05）. The maximal relaxing pressure was formed at the circumference of 1 cm from the anal verge ( Table 1 ，Fig. 1 ). Patients with fecal incontinence
Neither longitudinal pressure gradients nor maximal relaxing pressure existed ( Table 2 ，Fig. 2 ).
Normal children
Asymmetric pressure distributed in eight channels at every different circumference in the anal canal. Significant differences existed were seen among some pressures of eight channels at the same circumference, which formed the pressure asymmetry. From the circumference of 3 cm to 2 cm to 1 cm, the relaxing pressure asymmetry gradient presented with the high pressure changed from the posterior to anterior anal canal (P<0.05) ( Fig. 1 ). Patients with fecal incontinence
No relaxing pressure asymmetry gradient was seen with unchangeable high pressure positions limited at L, R, LP and RP from the circumferences of 2 cm and 1 cm of the anal verge. For the 3 cm circumference, there were no significant pressure differences among the eight channels ( Fig. 1 ). Squeezing
Normal children
For the posterior and slightly right channels (P, LP, RP, R), there were longitudinal pressure gradients from 3 cm to 2 cm and to 1 cm (P<0.05), but no significant differences of pressure between 2 cm and 1 cm (P>0.05). For the anterior and slightly left channels (A, LA, L, RA), there were longitudinal pressure gradients from 3 cm to 2 cm to 1 cm (P<0.05). The maximal pressure was presented at 1 cm circumference for all the eight channels ( Table 1 , Fig.
3 ).
Patients with fecal incontinence
There were neither longitudinal pressure gradients of the eight channels nor maximcal squeezing pressure ( Table 2 , Fig. 4 ).
Normal children
An asymmetric pressure distribution of eight channels was seen at every different circumference in the anal canal. Significant differences existed among some pressures of the eight channels at the same circumference, from which the pressure asymmetry formed. From the circumference of 3 cm to 2 cm to 1 cm, the squeezing pressure asymmetry gradient presented with the high pressure changed from the posterior to the anterior anal canal (P<0.05) ( Fig.
3 ).
Patients with fecal incontinence
There was no squeezing pressure asymmetry gradient, and the unchangeable high pressure positions limited at L and LP from the circumferences of 2 cm and 1 cm from the anal verge. For the 3 cm circumference, there were no significant pressure differences among the eight channels ( Fig. 4 ).
DISCUSSION
In this study, we found there were not only the longitudinal pressure gradients of eight channels, but also the longitudinal pressure asymmetry gradient in the anal canal. The characteristic pressure asymmetry gradient showed that the high pressure changed from the posterior to the anterior anal canal, especially for the level of 2 cm to 1 cm from the anal verge, forming the maximal pressure and minimal pressure asymmetry at 1 cm circumference. Hence we would like to discuss the anatomic evidence of direction variation of pressure asymmetry and its clinical use.
In 1974, Sharfik［2，3］described the components and functional directions of the anal sphincter in detail. The deep portion of the external sphincter and the puborectalis formed a unit muscle that can not be separated or form a top loop. When the top loop was squeezed, the anorectal angel increased and the formed pressure asymmetry presented with maximum posteriorly and minimum anteriorly. The intermediate loop was composed of the superficial external sphincter, which was posteriorly inserted on the coccyx with a horizontally posterior direction to the anal canal. The base loop was composed of subcutaneous part of the external sphincter, which was anteriorly inserted into the skin. Oh and Kark［4］gave a more detailed description of the intermediate loop of the double-loop system: the subcutaneous external sphincter was closely related to the superficial external sphincter, and inserted posteriorly to the back of the coccyx. The top loop and intermediate loop partially overlapped laterally. Most of the external deep fibers showed a circle-like formation. Based on the double-loop theory, Williamson et al［5］suggested the concept of
composite zone of the anal canal, which was formed by the overlap of the deep and superficial external sphincters. A Maxican surgeon observed normal individual cadavers and patients with anorectal malformations through the posterior sagittal approach. He discovered that the levator contraction pulled the rectum forward, which was inserted into the ventral part of the coccyx and sacrum. External muscle complex contraction elicited an elevation of the anus, which was a significant bulk and inserted into the coccyx. The contraction of parasagittal fibers provoked a tendency to close the anus, which was not inserted into the coccyx. At the ventral of the anal canal, the levator and the external muscle complex can not be separated, so it was called “the s triated muscle complex”.［6-11］
Li et al［12］found that in normal children the dis-tances between the anal verge and the upper level of the puborectalis was 1.80 cm, while for the lower level it was 1.02 cm. We speculated that in the range from 2 cm to 1 cm the top loop is distributed, thus pulling the rectum anteriorly to form the anorectal angle. Then, the direction of anal sphincter pressure asymmetry is determined, i.e., posteriorly high pressure and anteriorly low pressure are fromed in the anal canal. The intermediate loop is probably located at 1 cm circumference from the anal verge, the muscle fibers may circle the anterior anal canal and be inserted into the coccyx. It can be used to determine the pressure asymmetry direction of high pressure anteriorly and low pressure posteriorly, which is opposite from the top loop. It is believed that on voluntary contraction, the three loops compress alternating segments of the anal canal opposite, which allow each loop to complete and potentiate the action of the other. Hence, an incomplete close of the anal canal created by one single loop contraction can be compensated by the following opposite contraction of the other. This kind of gradient of anal sphincter pressure asymmetry contributes greatly to the anal continence. In patients with fecal incontinence, there is no pressure symmetry gradient, but the high pressure is distributed unchangeably at L, R, LP and RP in the relaxing state, and LP and L in the state of contraction. The direct oppositely compression of the sphincter to the anal canal is absent for the patients with fecal incontinence, which leads to the incomplete close of the anal canal and may be one of the mechanisms for fecal incontinence.
We also have found that the anterior pressure 1 cm from the anal verge is greater than the posterior pressure of the same circumference and the posterior pressure 2 cm from the anal verge. It is the very position that the maximal pressure in the anal canal is formed，so it is called the center of the striated muscle complex. Possibly 1cm circumference from the anal verge is the position of this complex. It is this portion that determines the pressure asymmetry direction of this circumference. We conclude that it is necessary not only to repair the posterior sphincter of the anal canal to maintain the integrity of the top loop, but also to repair the anterior sphincter of the intermediate loop,
because the intermediate loop integrity contributes greatly to the contraction of the striated muscle complex.
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