In a patient with an anal fistula whose external opening lies in the right posterior quadrant 2 cm from the anal verge, where does Goodsall's rule predict the internal opening?

• A Right anterior quadrant at the dentate line
• B Directly radial from the external opening at the dentate line
• C Posterior midline at the dentate line ✓
• D Left anterior quadrant at the dentate line

Explanation

Goodsall's rule states that external openings behind the transverse anal line track along curved tracts to the posterior midline, while anterior openings within 3 cm of the verge track radially straight to the nearest crypt. A posterior quadrant opening therefore predicts a posterior midline internal opening. Option B applies only to anterior fistulas close to the verge, which is the single fact that kills the most tempting distractor.

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.