Goodsall's rule relates the external opening of an anal fistula to its internal opening. An Anal Fistula is an abnormal connection between the Epithelialised surface of the Anal canal and (usually the Perianal skin 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.
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. In medicine a fistula (pl fistulas or fistulae is an abnormal connection or passageway between two Epithelium -lined organs or vessels that normally do not connect In fields of Anatomy, anatomical terms of location are descriptive terms to help identify relative positions or directions within a species A coronal plane (also known as the frontal plane) is any vertical plane that divides the body into Anterior and Posterior (belly and back sections The anus is an opening at the opposite end of an Animal 's Digestive tract from the Mouth. 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. The anal canal is the terminal part of the Large intestine. It is situated between the Rectum and Anus, below the level of the Pelvic diaphragm An exception to the rule are anterior fistulas lying more than 3 cm. from the anus, which may open in the anterior midline of the anal canal.
The investigation of choice for anal fistulas is magnetic resonance imaging (MRI).
References
- Perianal sepsis at Surgical Tutor
- Philip H Gordon (2002). Principles and Practice of Surgery for the Colon, Rectum and Anus. Informa Health Care, 245. ISBN 0824742826.