American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What does Goodsall's rule state regarding the course of anal fistulae?

1. They always follow a straight path from the midline.

2. They course in a straight path anteriorly and a curved path posteriorly from the midline.

3. They are directly perpendicular to the anal canal.

4. All anal fistulae are equal in length and path.

The correct answer is: They course in a straight path anteriorly and a curved path posteriorly from the midline.

Goodsall's rule provides an important framework for understanding the anatomical behavior of anal fistulae and how their course relates to their location in relation to the midline of the anal canal. The rule posits that fistulae originating from the posterior quadrant (located posterior to a line drawn between the anus and the coccyx) tend to follow a curved path as they approach the anal canal, leading to a more complex trajectory. In contrast, those arising from the anterior quadrant travel in a more direct, linear manner towards the anal canal. This rule helps surgeons predict the potential course of an anal fistula based on its external opening. Understanding this anatomical behavior is crucial for effective surgical intervention, as it informs the approach taken during fistula repair. Recognizing that posterior fistulae often have a curved trajectory informs surgeons that they may need to navigate through a more complex anatomy than with those that are anterior. In the context of the other options, the assertion about fistulae following a straight path from the midline does not factor in the differentiating characteristics based on the anterior or posterior positions. The idea that all fistulae are perpendicular to the anal canal overlooks the various possible angles and pathways they can take. Lastly, the statement that all anal