Chapter 80 The Anus and Anal Canal

The anal canal starts at the level where the rectum passes through the pelvic diaphragm, where the rectal ampulla suddenly narrows, and ends at the anal verge. The muscular junction between the rectum and anal canal can be felt with the finger as a thickened ridge called the anorectal ring. The puborectalis muscle maintains the angle between the anal canal and rectum and is an important component in the continence mechanism. The external sphincter forms the bulk of the anal sphincter complex and, although traditionally it has been subdivided into deep, superficial and subcutaneous portions, it is a single muscle, which is variably divided by lateral extensions from the longitudinal muscle layer. The longitudinal muscle is a direct continuation of the smooth muscle of the outer muscle coat of the rectum, augmented in its upper part by striated muscle fibres originating from the medial components of the pelvic floor.

Multiple Choice Questions
Weblinks

Journal articles

https://jnccn.org/view/journals/jnccn/15/5S/article-p726.xml/ (free)

Human papillomavirus and the challenges and opportunities in relation to cervical, vaginal and anal cancers.

https://onlinelibrary.wiley.com/doi/10.1111/j.1463-1318.2008.01681.x/ (free)

Association of Coloproctology of Great Britain and Ireland (ACPGBI) position statement for the management of anal fissure, informing aetiology, diagnosis and management of this condition.

https://onlinelibrary.wiley.com/doi/full/10.1111/j.1463-1318.2007.01372.x/ (paid)

Association of Coloproctology of Great Britain and Ireland (ACPGBI) position statement for the management of anal fistula, detailing aetiology, diagnosis and management strategies for this condition.

Guidelines

https://onlinelibrary.wiley.com/doi/10.1111/codi.13709/ (free)

Association of Coloproctology of Great Britain and Ireland (ACPGBI) guideline for the management of anal cancer. This includes imaging modalities, treatment options (including surgical techniques), follow-up and salvage surgical resections.

https://onlinelibrary.wiley.com/doi/full/10.1111/j.1463-1318.2010.02494.x/ (paid)

Association of Coloproctology of Great Britain and Ireland (ACPGBI) guideline for the management of anal intraepithelial neoplasia. This guideline updates a protocol for the management of anal intraepithelial neoplasia and offers some recommendations for follow-up.

Videos

80.1 Defecating proctogram with rectal and small bowel contrast illustrating a grade 3 intrarectal intussusception

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