According to Goodsall's rule, a patient has a fistula-in-ano whose external opening lies at the 2 o'clock position within 3 cm of the anal verge. Where is the internal opening most likely to be found?

• A At the posterior midline of the anal canal
• B Directly radial to the external opening at the 2 o'clock position on the dentate line ✓
• C Radially opposite at the 8 o'clock position on the dentate line
• D At the anterior midline regardless of the external opening site

Explanation

Goodsall's rule states that an external opening lying anterior to a transverse line across the anus leads by a direct radial tract to an internal opening at the same clock position on the dentate line, provided it is within 3 cm of the verge. Openings posterior to the line, or anterior openings farther than 3 cm away, track by a curved tract to the posterior midline. The rule helps the surgeon find the internal opening and identify the internal sphincter defect.

Reference: Bailey and Love's Short Practice of Surgery, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.