Donald School Journal of Ultrasound in Obstetrics and Gynecology

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VOLUME 5 , ISSUE 4 ( October-December, 2011 ) > List of Articles


Ultrasound Assessment of the Internal Anal Sphincter in Women with Fecal Incontinence and Posterior Vaginal Wall Prolapse (Rectocele)

Hossam H Kamel, Ahmad G Serour, Laila AS Mousa

Keywords : Three-dimensional ultrasound (3D US),Fecal incontinence (FI),Internal anal sphincter (IAS),External anal sphincter (EAS),Collagen,Rectocele,Central nervous system (CNS)

Citation Information : Kamel HH, Serour AG, Mousa LA. Ultrasound Assessment of the Internal Anal Sphincter in Women with Fecal Incontinence and Posterior Vaginal Wall Prolapse (Rectocele). Donald School J Ultrasound Obstet Gynecol 2011; 5 (4):339-342.

DOI: 10.5005/jp-journals-10009-1211

License: CC BY-NC 4.0

Published Online: 01-09-2012

Copyright Statement:  Copyright © 2011; The Author(s).


Rupture of the internal anal sphincter (IAS) causes its weakness and it will not withstand increases of abdominal pressure, and fecal incontinence (FI) will occur. Recently, we put forward a novel concept on the physiology of defecation. Defecation is divided into two stages: First stage before training and second stage starts at the age of about 2 years, when the mother starts to teach her child how to hold up himself. This is gained by maintaining high alpha-sympathetic tone at the IAS, thus keeping it closed all the time till there is a need to pass stool or flatus, and the time and place are convenient. On defecation, six neuromuscular actions take place under the control of the CNS: (1) The person will relax the external anal sphincter, (2) he will lower the gained high alpha-sympathetic tone at the IAS, thus opening the anal canal, (3) he will relax the pelvic floor muscles bringing the rectum and the anal canal into one axis, (4) the abdominal and diaphragmatic muscles contract to increase the abdominal pressure, (5) the muscles of the distal colon and rectum contract pushing the stool, (6) sequential contractions of the three parts of the external anal sphincter (EAS) that squeeze any residual contents in the anal canal. Thus, the anal canal is closed and empty under normal circumstances. The IAS is a collageno-muscular tissue cylinder that surrounds the anal canal.

The IAS is intimately related to the posterior vaginal wall, and the vagina is over stretched in labor, childbirth trauma affects both the posterior vaginal wall and the IAS. Rupture of the collagen sheet of the IAS which causes its weakness is better demonstrated by imaging by 3D US.

Normal vagina is a cylinder of collageno-elastic-muscular tissues. Its strong collagen sheet is responsible for keeping it in its normal upward position. Labors cause redundancy and weakness of the vaginal walls with subsequent prolapse; and lacerations of the IAS which is closely related to the posterior vaginal wall leading to FI.

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  1. Fecal incontinence: A novel concept. The role of the internal anal sphincter (IAS) in defecation and fecal incontinence. Gynaecologia et Perinatologia April-June 2010;19(2):73-128.
  2. Imaging the internal urethral sphincter and the vagina in normal women and women suffering from stress urinary incontinence and vaginal prolapse. Gynaecologia et Perinatologia, October-December. Gynaecologia et Perinatologia, October-December 2009;18(4):169-286.
  3. Surgical treatment of stress urinary incontinence (SUI), fecal incontinence (FI) and vaginal prolapse by a novel operation, “urethroano-vaginoplasy” stress urinary incontinence (SUI), fecal incontinence (FI) and vaginal prolapse: A novel concept on their pathophysiology and their surgical treatment. Gynaecologia et Perinatologia July-September. Gynaecologia et Perinatologia July-September 2010;19(3):129.
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  5. Primary sphincter repair: Are the results of the operation good enough? Dis Colon Rectum 2004;47:18-23.
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  7. Lower genital tract and anal sphincter trauma. Best Pract Res Clin Obstet Gyecol 2002;16:99-115.
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