Intersphincteric Abscess

An intersphincteric abscess lies between the internal and external anal sphincters.

It develops directly from an infected anal gland and may extend inferiorly to become a perianal abscess or superiorly toward the supralevator space.

Because the collection is deep, external swelling may be absent.

Patients typically have severe deep anal or rectal pain with little visible external abnormality.

Pain may worsen with defaecation or digital examination.

Rectal examination can identify focal tenderness or a deep fluctuant area, although examination may require anaesthesia because of pain.

Fever and urinary retention may occur.

MRI or CT is appropriate when the location is not clinically clear or deeper extension is suspected.

Drain promptly.

An intersphincteric collection is generally approached through the anal canal into the intersphincteric space, allowing drainage without creating an unnecessary tract across the external sphincter.

Do not drain a purely intersphincteric abscess through the ischioanal fossa because this can create a more complex fistula.

Assess for upward extension toward the supralevator space and downward extension into superficial tissues.

Antibiotics are reserved for systemic infection, significant cellulitis or immunocompromise after drainage.