Quick answer: An anal abscess is a collection of pus near the anus; an anal fistula is a tunnel that may remain after an abscess. Increasing anal pain, swelling or fever needs urgent assessment, and an abscess often needs drainage. Persistent discharge or recurrent swelling warrants assessment for an anal fistula NHS anal fistula guidance.
Anal abscess: when to seek urgent care
A painful swelling near the anus, constant throbbing pain, fever or feeling unwell can signal an abscess. Seek urgent medical assessment rather than squeezing it or waiting for it to burst. Drainage is often required; antibiotics alone may not resolve the collection. After treatment, persistent discharge or recurrent swelling may indicate a fistula. NHS explanation of abscess and fistula.
What is it?
Most fistulas develop after an anal gland abscess. They cause discharge, irritation and recurrent infection.
Investigations
Clinical examination, MRI of the pelvis to map the tract and a careful examination under anaesthesia.
Traditional repair
Fistulotomy — laying the tract open. Effective for simple low fistulas but unsuitable for high or complex tracts.
Sphincter-preserving options
VAAFT (video-assisted), LIFT, fibrin glue or seton placement — chosen based on anatomy.
Recovery
Day-care or one-night admission. Healing over 4–6 weeks with regular reviews.