Accurate Localization of the Internal Opening in a Cryptoglandular Anal Fistula: Complementary Roles of Goodsall's Rule, MRI, and Intraoperative Assessment: A Case Report.

Accurate localization of the internal opening is essential for successful surgical management of cryptoglandular anal fistulas. Although Goodsall's rule remains a useful clinical guide, accurate delineation of fistula anatomy often requires complementary assessment with magnetic resonance imaging (MRI) and intraoperative evaluation. We report the case of a 34-year-old healthy man presenting with a recurrent perianal fistula characterized by intermittent swelling and purulent discharge. The external opening was located at the 2 o'clock position, more than 3 cm from the anal verge. Preoperative MRI demonstrated a curved transsphincteric fistulous tract extending to an internal opening at the posterior midline without secondary extensions or abscess. The internal opening was confirmed intraoperatively by clinical assessment and hydrogen peroxide injection through the external opening. The extrasphincteric portion of the tract and surrounding chronically inflamed tissue were excised (partial fistulectomy), whereas the transsphincteric portion crossing the external anal sphincter was treated by lay-open fistulotomy to minimize additional sphincter tissue sacrifice. The postoperative course was uneventful, with complete wound healing within 2 months and no impairment of continence. This case illustrates that accurate localization of the internal opening is best achieved through the complementary use of clinical assessment, Goodsall's rule, MRI, and intraoperative confirmation, thereby facilitating appropriate surgical planning and sphincter-preserving treatment.