Anal fistula, or fistula-in-ano, is an abnormal connection between the epithelialised surface of the anal canal and (usually) the perianal skin. 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 You can get a fistula as a result of an infection or an abscess (collection of pus). It can also be caused by conditions that affect the bowel such as Crohn’s disease. If you are diagnosed with a fistula, you will also be tested for Crohn’s, as unfortunately the two go hand in hand. Crohn’s sufferers are more prone to developing fistulas.
Fistulas most often occur as a result of one or more perianal abcesses. A perianal fistula is a collection of pus under the skin next to the anal canal (back passage). It is usually caused by an infection of the glands of the anal canal. This presents as a painful lump in the area and may be associated with a fever. The treatment involves drainage of the pus usually by operation. Some of these infections go on to form a longstanding fistula (a track running from the skin near the anus to the inside of the anal canal). These intermittently swell and discharge pus and blood. The treatment involves surgery to either open the track to the skin or close the inside opening. In laymans terms, a fistula is a tunnel that connects two organs or vessels that normally wouldn’t be connected. The fistulas need to be treated and closed off with surgery. There are different techniques used in surgery to do this. But before a fistula can be closed off, it needs to be kept open to ensure that all infection and pus from the abcesses has been drained. To keep the fistula open, surgeons will insert a seton under general anesthetic. A seton is a surgical cord that is run into the fistula opening, through the fistula track, out the anus and then tied together, so essentually it runs around in a loop. This stops the fistula opening closing up and allows the pus to drain out over time so that there is no longer any infection inside the fistula.
If you have a ‘shallow’ fistula that is close to the surface of the skin and doesn’t run through any muscle, the surgeons are usually able to tighten the seton over time until it eventually comes out altogether as the fistula heals. However, if you have a more complicated fistula that runs through muscle and is not close to the surface, you will then need corrective surgery. Fistula sufferers live each day with the seton in their body. You could even have more than one seton, depending on how many fistulas you have. At first they are difficult to live with, it can be uncomfortable to sit down, walk and go to the toilet. However, like everything, you will get used to living with a seton and will work out your own ways to deal with it. There are some tips on living with setons on the ‘ Tips and Advice’ page.