Anal fistula is an abnormal connection between the inside of the bowel, the anal canal, and the skin of the anus. It is normally the result of an infection around the anus which develops into a collection of pus, called an abscess, in the nearby tissue. Once the pus has drained away, it can leave a small channel behind, which then may require surgery.
Symptoms usually include skin irritation around the anus area, pain that gets worse when the patient sits down, moves around, has a bowel movement, or coughs, stools which contain pus or blood, smelly discharge from the anus, swelling and redness around the anus, a fever especially if the patient has an abscess, and bowel incontinence.
They are usually caused by an abscess in the anal glands which then discharges to the outside and instead of healing, it leaves an abnormal connection between the skin and the anal canal. Other, less common, causes can include if a patient has a related gastric condition, such as Crohn's disease, which causes inflammation in the digestive system, or diverticulitis, which causes infection in the small pouches of the large intestine. Rarer causes can involve hidradenitis suppurativa, a skin condition causing abscesses and scarring, infection with tuberculosis or HIV, or a complication following surgery near the anus.
Usually a patient will undergo a clinical diagnosis in an outpatient clinic, during which the doctor will examine the patient's symptoms. If there is any doubt, it can be further clarified through the use of an MRI scan.
Other tests that may be used include a proctoscopy or a flexible sigmoidoscopy. A proctoscopy is a procedure which examines the inside of the anal canal by inserting a short instrument into the anus to hold it open whilst the doctor inspects the lining of the anus. A flexible sigmoidoscopy is a procedure which involves the use of a thin, flexible tube which has a camera inside it to look further inside the bowel.
Surgery usually falls into two categories, depending on the nature of the fistula. Simple fistulas, in which there is a connection between the skin and the anal canal but does not involve much or any of the anal sphincter, the muscle that controls continence, are treated by laying open the fistula. This procedure, known as fistulotomy, involves connecting the two ends together and allowing the subsequent wound to heal up spontaneously.
The second category of surgery is when the sphincters are more complex and involve the anal sphincter, which if cut the patient then becomes incontinent. There are a variety of surgical techniques that can be used, including:
- The insertion of a seton, which is a piece of surgical thread that is left in the fistula for a number of weeks to keep it open, allowing it to drain and heal, while preventing the need to cut the sphincter muscles;
- Advancement flap procedure, which involves cutting or scraping out the fistula and covering the hole at the point it entered the bowel with tissue taken from inside the rectum;
- Bioprosthetic plug, which is when animal tissue is used to construct a cone-shaped plug inserted to block the internal opening of the fistula;
- Ligation of the intersphincteric fistula tract (LIFT), which is a relatively new form of treatment and involves an incision in the skin above the fistula, and the sphincter muscles are moved apart.
The benefit is to stop the patient having an unpleasant discharging wound near the anus, and surgery will help heal the fistula completely. It is very unpleasant living with a discharge that the patient cannot control or experience recurrent abscesses, which can sometimes become infected and further abscess can develop. Surgery will address this and help ensure the patient has the best quality of life as possible.
As with any case of surgery, there will be many possible risks and side effects involved, albeit very rare. The principal risks of anal fistula surgery, however, include damage to the anal sphincter, recurrence of the fistula, some degree of bowel incontinence, and infection. Patients may require further treatment to address these issues, including a course of antibiotics, and in more severe cases, treatment in hospital.
General surgeons, particularly those specialised in colorectal disease. They would treat the simple fistulas, whilst the more complex fistulas would be treated in specialist hospitals.
There is not much patients need to prepare, other than eating nothing prior to the operation. Some surgeons may ask patients to take laxatives or enemas to clear out the bowel, but this is not essential. A general anaesthetic will likely be given for surgery, which can make some patients sick so it is important that they do not eat or drink anything for six hours before the procedure.
Patients could live with the fistula without undergoing surgery, but this would be very unpleasant. In terms of the non-surgical procedures, there is the option of applying a special glue, called fibrin glue, into the fistula while the patient is under a general anaesthetic. The glue will help seal the fistula and encourage it to heal. Whilst this is considered a less effective way to treat fistulas, it is a viable alternative to surgery.
The operation is usually conducted under general anaesthesia meaning the patient will be unconscious and asleep during the procedure. After the operation, the patient will usually be able to return home the same day.
The patient will need to rest until the effects of the anaesthetic have worn off, but they will likely experience some level of discomfort until this happens. There is likely also to be a small amount of bleeding following the operation. It is very important the patient has someone who can take them home afterwards, and someone who can take care of them until the anaesthesia has worn off.
Usually after fistula surgery there is an open wound which takes around six to eight weeks to heal up. In patients with more complex fistulas there may be multiple stage procedures that could go on for months, even sometimes years.
Patients are prescribed medicine for pain relief. Antibiotics may be required for some patients, especially those with diabetes or decreased immunity. Patients will be able to move around, eat and drink once the anaesthetic has worn off. Stool softeners may be prescribed to ease any discomfort experienced during bowel movements. Having warm baths, without any soap or other substances, is often recommended to keep the wound clean and ease pain and discomfort for patients.
In general, if the anatomy is well known and the surgery is straightforward, most of the fistulas will heal up and there should be no further issues. However, there are a number of complications which can occur as a result of surgery, including bleeding, bowel incontinence, the wound taking a long time to heal, constipation and difficulty opening the bowels, urinary retention, and narrowing of the anal canal. Sometimes these fistulas are more complicated than they appear and they can recur later.