An anal fistula is a abnormal tunnel that connects the inside of the anal canal to the skin near the anus. It most often develops after a perianal abscess, when a track is left behind as the infection heals. Fistulas tend not to clear on their own and usually need a procedure to settle them, but with careful assessment and treatment the outlook is good.
What causes an anal fistula?
A previous abscess
The most common cause, leaving a track behind as it heals.
Blocked anal glands
Infection in these small glands starts the process.
Inflammatory bowel disease
Less commonly linked, particularly Crohn's disease.
Recurrent infection
Repeated abscesses in the same area.
Rarely
Previous surgery or injury to the region.
When to seek assessment promptly
Ongoing discharge of pus or blood near the anus
Abscesses that keep coming back in the same place
Skin irritation or a persistent opening near the anus
A throbbing ache that eases when the area discharges
Symptoms that follow a previously drained abscess
How it is treated
Mr Kimble examines the area and, where needed, arranges an MRI scan or an examination under anaesthetic to map the fistula precisely. The right operation depends on the path the fistula takes and how it relates to the muscles that control continence. Options range from laying open a simple, low fistula, to placing a soft drainage stitch called a seton, or using sphincter-preserving techniques for more complex tracks. Protecting bowel control is a key priority throughout. Many fistulas are treated as day cases, with wound care over the following weeks and review to check healing.
If the area becomes very painful, hot and swollen, or you develop a fever, seek medical advice promptly, as this can indicate a new abscess that needs draining.