Jung Sung-Ae, Pretorius Dolores H, Weinstein Milena, Nager Charles W, Den-Boer Debbie, Mittal Ravinder K
Division of Gastroenterology, Pelvic Floor Function and Diseases Group, University of California, San Diego, California 92161, USA.
Dis Colon Rectum. 2008 Jun;51(6):932-9. doi: 10.1007/s10350-008-9221-8. Epub 2008 Mar 11.
To describe the functional correlates of anal canal anatomy using 3 dimensional ultrasound imaging.
Ten nulliparous women were studied by using a 10-cm bag of 20-mm diameter. The bag was placed along the anal canal and inflated with 20 to 45 ml water, in 5-ml increments. At each volume, a three-dimensional ultrasound volume of the anal canal was obtained while the subjects were at rest and squeeze. The ultrasound images were analyzed to determine the relationship between the bag cross-sectional area and bag pressure.
At low distension volumes, the bag is shaped like an "hourglass." The flared ends of the funnels correspond with the proximal and distal margins of the puborectalis muscle and external anal sphincter respectively. With increasing bag volumes, the length of completely closed segment of anal canal decreased. The last anal segment to open at rest was the one surrounded by all three structures. Anal contraction resulted in reduction of the anal canal cross-sectional area; the least compliant part of the anal canal was the one surrounded by external anal sphincter.
The internal anal sphincter, external anal sphincter, and puborectalis muscle are all involved in the anal canal closure function. During contraction, the external anal sphincter is the strongest component of anal canal closure mechanism.
使用三维超声成像描述肛管解剖结构的功能相关性。
对10名未生育女性使用一个直径20毫米、长10厘米的袋子进行研究。将袋子沿肛管放置，以5毫升的增量注入20至45毫升水使其膨胀。在每个容量下，当受试者处于静息和挤压状态时获取肛管的三维超声容积。对超声图像进行分析以确定袋子横截面积与袋子压力之间的关系。
在低扩张容量时，袋子呈“沙漏”形。漏斗的扩口端分别对应耻骨直肠肌和肛门外括约肌的近端和远端边缘。随着袋子容量增加，肛管完全闭合段的长度缩短。静息时最后开放的肛管节段是被所有这三种结构包围的节段。肛门收缩导致肛管横截面积减小；肛管最不易扩张的部分是被肛门外括约肌包围的部分。
肛门内括约肌、肛门外括约肌和耻骨直肠肌均参与肛管闭合功能。在收缩过程中，肛门外括约肌是肛管闭合机制中最强的组成部分。
