A 35-year-old man has a recurrent perianal fistula with an external opening in the right posterior quadrant close to the anal verge. According to Goodsall's rule, where will the internal opening be found?
- A In the posterior midline ✓
- B Directly radial to the external opening in the anal canal
- C In the anterior midline
- D At the dentate line opposite the external opening on the left side
Correct answer: A. In the posterior midline
Explanation
Goodsall's rule states that if the external opening lies behind a transverse line drawn across the anus, the tract curves to open in the posterior midline, reflecting the horseshoe arrangement of the postanal space. Only external openings anterior to the line open radially directly into the anal canal. Since this opening is posterior, the curved posterior midline course applies, and the radial option would only be correct for an anterior fistula.
Reference: Bailey and Love's Short Practice of Surgery, 28th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.