A 32-year-old man has recurrent perianal discharge. Examination reveals an external opening 4 cm from the anal verge in the postero-lateral position at the 5 o'clock orientation relative to the anus. According to Goodsall's rule, where will the internal opening be found?

• A Directly radial from the external opening in the anal canal
• B In the posterior midline of the anal canal ✓
• C In the anterior midline of the anal canal
• D At the level of the puborectalis sling laterally

Explanation

Goodsall's rule states that an external opening behind the transverse anal line opens into the anal canal in the posterior midline, usually through a curved tract. Only openings anterior to the transverse line open radially into the nearest crypt, and even anterior openings more than 3 cm from the verge may still track to the posterior midline. This predicts tract anatomy before fistulotomy.

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.