intersphincteric

Intersphincteric refers to a location or plane between two sphincters, most commonly the internal anal sphincter and the external anal sphincter. In medical contexts it is used to describe processes or structures that lie within this intersphincteric space, or to describe surgical approaches that navigate or treat lesions in that plane. The term can also apply to conditions such as intersphincteric abscess or intersphincteric fistula, where infection or tract formation occurs within this space.

Anatomy and boundaries

The intersphincteric space is a potential space situated between the internal anal sphincter (IAS) and the external anal sphincter (EAS). It extends from the anal canal at the level of the dentate line up toward the pelvic floor, and is bounded medially by the IAS and laterally by the EAS. The space may contain loose connective tissue and small accessory glands. In disease, an inflammatory process can track within this plane, creating a fistulous tract or abscess without breaching the external sphincter complex.

Clinical relevance

Intersphincteric disease most often relates to fistula-in-ano, particularly the intersphincteric type in which the tract runs between the IAS and EAS and opens internally into the anal canal, with an external opening on the perianal skin. It is the simplest fistula configuration in several classification schemes and has important implications for continence preservation.

Diagnosis and management

Evaluation typically involves clinical examination with anoscopy, supported by imaging such as magnetic resonance imaging (MRI) or endoanal ultrasound to delineate tract anatomy. Management ranges from intersphincteric fistulotomy or fistulotomy with tract laying open for straightforward, low fistulas, to more complex procedures or staged strategies for higher disease to minimize continence risk.