A anal fistula is a track connecting the internal anal canal to the skin surrounding the anal orifice. This is due to infection usually of the glands lining the anal canal which if infected becomes trapped and burrows its way to the anal skin forming a fistula, sometimes it doesn’t break through the skin and forms a painful swelling(abscess).
Anal pain and swelling(Abscess)
Recurrent discharge of fluid or blood.
Assessment at the bedside with “glove” examination and sigmoidoscopy is usually sufficient.
Anorectal USS, CT scan, fistulogram and MRI may be used in complex cases.
In almost all cases involves drainage of infection (drain abscess, draining seton, insertion of mushroom catheter) and subsequently eradication of the track which involves LAY OPEN, or in complex cases tightening SETON or RECTAL ADVANCEMENT FLAP. Preservation of the function of the anal sphincter muscle is a high priority to avoid incontinence.
Anorectal cancer and Crohns disease can present as anal sepsis or fistula so follow up is strongly recommended.