Anal fistula, or fistula-in-ano, is an abnormal connection between
the epithelialised surface of the anal canal and (usually) the perianal
Anal fistulae originate from the anal glands, which are located
between the two layers of the anal sphincters and which drain into
the anal canal. If the outlet of these glands becomes blocked, an
abscess can form which can eventually point to the skin surface.
The tract formed by this process is the fistula.
Abscesses can recur if the fistula seals over, allowing the
accumulation of pus. It then points to the surface again, and the
An anal fistula can cause bleeding and discharge when passing stools - and
can be painful.
An anal fistula can occur after surgery to drain an anal abscess.
In some cases, an anal fistula causes persistent drainage. In other cases,
where the outside of the channel opening closes, the result may be
recurrent anal abscesses. The only cure for an anal fistula is surgery.
Symptoms of anal fistulas
Possible symptoms include:
Pain, which is usually constant, throbbing and worse when sitting down
Skin irritation around the anus, including swelling, redness and tenderness
Discharge of pus or blood
Constipation or pain associated with bowel movements
Diagnosis of anal fistulas
Usually, a clinical evaluation - including a digital rectal examination - is
sufficient to diagnose an anal fistula, but some patients may require additional
tests to screen for:
Sexually transmitted infections
Inflammatory bowel disease
In rare cases, an examination may be done under anaesthesia. The doctor may
also ask for an ultrasound, a CT scan or an MRI.
There are several stages to treating an anal fistula:
Definitive treatment of a fistula aims to stop it recurring. Treatment depends on
where the fistula lies, and which parts of the anal sphincter it crosses
Doing nothing — a drainage seton can be left in place long-term to prevent
problems. This is the safest option although it does not definitively cure the
Lay-open of fistula-in-ano — this option involves an operation to cut the
fistula open. Once the fistula has been laid open it will be packed on a daily
basis for a short period of time to ensure that the wound heals from the inside
Cutting seton — if the fistula is in a high position and it passes through a
significant portion of the sphincter muscle, a cutting seton (from the Latin seta,
"bristle") may be used. This involves inserting a thin tube through the fistula
tract and tying the ends together outside of the body.
Seton stitch — a length of suture material looped through the fistula which
keeps it open and allows pus to drain out. In this situation, the seton is referred
to as a draining seton.
Fistulotomy — till anorectal ring
Colostomy — to allow healing
Fibrin glue injection is a method explored in recent years, with variable
success. It involves injecting the fistula with a biodegradable glue which should,
in theory, close the fistula from the inside out, and let it heal naturally. This
method is perhaps best tried before all others since, if successful, it avoids the
risk of incontinence, and creates minimal stress for the patient
Endorectal advancement flap is a procedure in which the internal opening of
the fistula is identified and a flap of mucosal tissue is cut around the opening.
The flap is lifted to expose the fistula, which is then cleaned and the internal
opening is sewn shut.
Laying open abscesses and secondary tracts
Adequate drainage – seton insertion
Openings and tracts
Internal and External
Single –v- multiple
Extensions / Horseshoe
Relation to sphincter complex
High –v- Low
Exclude co-existent disease
MRI FOR FISTULA-IN-ANO
HALLIGAN Radiology 2006Abscesses &
Contralateral disease Other pathology
Fistula tract identified with probe
Extent of external sphincter involvement
Tract and muscle divided
Secondary tracts laid open
+/- marsupialisation wound
SURGICAL OPTIONS –
Lay open external tract
Draining seton replaced with cutting seton
1/0 Prolene suture
Tied tight around sphincter complex
Simultaneous slow cutting and repair of
May require re-tightening
SURGICAL OPTIONS – CUTTING
•Core out tract
•Direct visualisation of secondary tracts
•Sphincter repair +/- advancement flap
SURGICAL OPTIONS –
Some patients will have active infection when they present with a fistula, and this
requires clearing up before definitive treatment can be decided.
Antibiotics can be used as with other infections, but the best way of healing infection is to
prevent the buildup of pus in the fistula, which leads to abscess formation. This can be
done with a seton..
Japan: A man suffering from
anal fistula. From the Yamai no
Soshi, late 12th century…
THANK YOU FOR YOUR ATTENTION
Kshara, a traditional ayurvedic medicine treatment for fistulae and
piles (inflamed hemorrhoids) consisting of herbs, has been in use
in India for about 5000 years. This treatment is mentioned in
ancient medical texts.
Taishan Medical University
Cell# : 008615269868530