An anal fistula is an abnormal passage that extends from the anal canal to the skin around the anus. It usually develops from a previous abscess or infection in the region that had either drained by bursting through the skin or was incised surgically to effect drainage and did not heal properly.
Besides developing from anal abscesses, anal fistulas are also common in those with inflammatory bowel disease, diverticulitis (infection of small pouches that sometimes develop in the colon), surgery in the region of the anus, tuberculosis, HIV and hidradenitis suppurativa, a chronic skin condition that frequently causes abscesses in the skin.
People suffering with an anal fistula may experience the following symptoms
- An opening may be seen or felt near the anus
- Discharge of faeces, pus and sometimes blood occurs from the opening
- Anal discomfort
- Skin irritation and inflammation
- Difficulty with bowel movements
Your doctor will take a full history and carry out a clinical examination. Usually this will involve a rigid sigmoidoscopy and sometimes a proctoscopy as well. Often, if the doctor is able find the inner and outer openings of the fistula, no special investigations will be required.
If it is not possible to find the fistula or if the problem is longstanding or recurrent, an MRI scan or endoanal ultrasound scan will be recommended.
Sometimes the area may be too uncomfortable to examine. Your doctor may then recommend carrying out an examination under anaesthesia to confirm the diagnosis, and possibly start fistula treatment at the same time.
If you are over the age of 40 and have had any bleeding or change in bowel habits, your doctor may recommend endoscopic examination of the bowel either by flexible sigmoidoscopy or colonoscopy to ensure that it is otherwise healthy, alongside treating the fistula.
An anal fistula does not usually heal without surgical treatment. Leakage of faeces can be unpleasant and lead to irritation and infection.
Anal fistulas usually require surgical treatment to heal. They often pass through the muscles surrounding the anus that are important for maintaining continence. It is very important that when fistulae are treated these muscles are not damaged as it can lead to loss of bowel control.
Fistula surgery can be difficult, and some patients may require repeated procedures to properly heal the fistula.
There are several surgical options that can be used:
Fistulotomy: This involves cutting out the fistula track. It is useful for those fistulae that don't pass through the sphincter muscle or only through a small part of it.
Seton Drainage: Simple drainage involves the insertion of a drainage tube known as a seton through the fistula track. This can stay in place long term but is frequently used for a few weeks only. This allows inflammation to settle, so that curative surgery can be planned
Cutting Seton: This involves using a piece of tubing or seton which is placed through the fistula and tied firmly around the sphincter muscle. This tubing is tightened up every 2-3 weeks.
Fistula plug or fistula paste: This is a newer technique and involves inserting a plug of collagen material or injecting collagen paste into the fistula track.
Muscle Sparing Laser Treatment (With FiLaC®): To treat anal fistulas as muscle-sparing as possible, FiLaC® laser therapy of the fistula tract is also offered.
Fistulotomy is usually a day surgery performed under general anaesthesia. Your doctor may use an instrument to probe the fistula and identify its course and where it opens. Dye may also be passed through the fistula to help identify its opening. A fistulotomy is performed if the fistula does not pass through the anal muscles that keep the bowel continent or it passes through them very minimally. During the procedure, the fistula track is incised to form an open wound which closes the track upon healing. The wound is encouraged to heal from the base upwards. A bandage is placed in the upper region of the wound to prevent it from closing over and forming another fistula.
If the fistula passes significantly high up through the sphincter muscles, your doctor may recommend insertion of a seton tube as a fistulotomy in this region could lead to complications such as bowel incontinence. The seton is a thin piece of tubing or silk that may be left in the fistula to permit drainage of the area and healing of the tissues until corrective surgery can be performed. A cutting seton is a technique used to remove the fistula. During this procedure one end of the seton is passed through the external opening of the fistula and brought out through the internal opening and anus. It is then tied to the other end coming out of the external opening thus looping around the sphincter muscle. The seton is tightened every 2-3 weeks and slowly cuts through the sphincter muscle it encloses gradually shifting the fistula track lower until it is laid open and the seton falls off. The shallow wound then heals on its own and the integrity of the sphincter muscle is maintained. It usually takes about 4-8 weeks for the seton to fall off.
Before surgery, you will receive a complete medical evaluation. Your doctor will discuss your surgery in detail. You should notify your doctor of any allergies or any medications you are taking. You may be asked to stop taking certain medications temporarily. The location of the fistula and its relationship with the anal sphincter muscles is evaluated either preoperatively or at the beginning of surgery to help decide the appropriate procedure for treatment.
Following a fistulotomy. you will experience some pain for which your doctor will prescribe medications. You should take these regularly for the first 48 hours and then as needed. You may not experience a bowel movement for 2-3 days after the procedure. Though you may have increased pain with bowel movements you are advised to empty your bowels normally. The wound should be cleaned and dressed daily. Make sure you include fibre in your diet and drink plenty of water so that your stools are not hard. A certain amount of blood and discharge can be expected following the procedure. There may be some swelling in the region around the anus. You can resume normal physical activity as tolerated. Strenuous activity such as sports can be resumed in a couple of weeks. Avoid smoking as it can delay healing.
Following a seton procedure, you should try to keep the area clean and dry but avoid scrubbing excessively as it can make the tissues sore. A light dressing can be placed over the area. Avoid strenuous activity, heavy lifting and sexual intercourse for at least 2 weeks.
Down-time, lifestyle or off-work duration
Recovery after a fistulotomy may take 3-12 weeks.
A fistulotomy is ideal treatment for an uncomplicated anal fistula that does not involve much of the anal sphincter muscles. The cutting seton technique is ideal for high anal fistulae as it preserves the integrity of the sphincter muscles while removing the fistula. Some people may experience gas or liquid stool incontinence, recurrence of the fistula or an abscess following treatment.