Goodsall's rule
Goodsall's rule relates the external opening of an anal fistula to its internal opening. It states that the external opening situated behind the transverse anal line will open into the anal canal in the midline posteriorly. An anterior opening is usually associated with a radial tract. Or in more direct terms, it means that anterior-opening fistulas tend to follow a simple direct course while posterior-opening fistulas may follow a devious, curving path with some even being horseshoe-shaped before opening in the posterior midline.[1]
Fistulas can be described as anterior or posterior relating to a line drawn in the coronal plane across the anus, the so called transverse anal line. Anterior fistulas will have a direct track into the anal canal. Posterior fistulas will have a curved track with their internal opening lying in the posterior midline of the anal canal. An exception to the rule are anterior fistulas lying more than 3 cm. from the anus, which may have a curved track (similar to posterior fistulas) that opens into the posterior midline of the anal canal.
The investigation of choice for anal fistulas is magnetic resonance imaging (MRI).
Goodsall's rule is named after David Henry Goodsall who described it in 1900.
References
- Perianal sepsis at Surgical Tutor
- Philip H Gordon (2002). Principles and Practice of Surgery for the Colon, Rectum and Anus. Informa Health Care. p. 245. ISBN 0-8247-4282-6.
- ^ Burgess BE. Chapter 88. Anorectal Disorders. In: Tintinalli JE, Stapczynski JS, Cline DM, Ma OJ, Cydulka RK, Meckler GD, eds. Tintinalli's Emergency Medicine: A Comprehensive Study Guide. 7th ed. New York: McGraw-Hill; 2011. http://www.accessmedicine.com/content.aspx?aID=6361536. Accessed June 14, 2012.
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