Anal fistula
What is an anal fistula?
An anal fistula is an abnormal communication between the inside of the anus and the skin close to it. On the surface of the skin around the anus there may be one or more holes evident: these are the external openings of thin passages which tunnel down towards the anal canal.
What causes an anal fistula?
The usual cause of this is an infection of the glands close to the anus which produce mucus to lubricate the anus. An infection can lead to a localised collection of pus called an abscess.
When an abscess has discharged itself or has been lanced (“drained”) the skin will usually heal over. Sometimes, however, a small hole is left on the outside. This usually means that a tunnel (a “fistula”) has developed between the anal gland and the outside opening. Only a minority of people who have had an abscess will go on to develop a fistula.
Other conditions such as Crohn’s disease can also be the cause of anal fistulas.
What are the symptoms of an anal fistula?
Quite often the fistula comes after an abscess in the region and the symptoms are of a discharge from a small hole near the anus. The discharge can be pus, blood or even small amounts of faeces.
Pain is not a common feature of a fistula. If there is pain it may imply that there is an ongoing abscess that will require more urgent attention.
How is an anal fistula diagnosed?
Your doctor will take a history and examine you. Quite often the diagnosis can be made without further investigation. Sometimes the best way to properly examine a fistula is under a general anaesthetic. This is because an internal examination can be uncomfortable.
Occasionally an MRI scan is required to better understand the anatomy and to guide treatment.
If there is any doubt about the underlying cause, your doctor may also arrange some investigations to rule out the diagnosis of crohn’s disease. This would include the use of a colonoscopy or a CT scan of the abdomen.
How is an anal fistula treated?
The majority of anal fistulae can be easily treated, however this treatment needs to be performed by an expert.
Surgery
The most effective treatment involves cutting through the fistula and a small amount of the muscle of the bottom known as the sphincter muscle. This is known as ‘laying open’. This has the highest chance of cure but is not suitable to treat all fistulas as sometimes it can result in minor incontinence.
In this situation, the surgeon may recommend placing a thread through the fistula. This allows the fluid to drain without collecting around the anus. This procedure is called placing a seton. This does not heal the fistula but allows the symptoms to settle before more definitive surgery can be offered.
In rare cases the fistula can be more complex to treat. Under these circumstances your surgeon will discuss other treatment options with you. It is important to understand that you may require multiple operations to treat the fistula under these circumstances.
Minimally invasive options include the use of a fistula plug, laser treatment or video assisted treatment irrigation and washing of the fistula tract. All of these treatments are available at one wellbeck street and which procedure is suitable for any fistula will depend on characteristics of the fistula. More invasive treatments include procedures to remove the fistula tract, known as a LIFT procedure or a plastic surgery procedure called an advancement flap.
If you have Crohn’s disease, the treatment of fistulas can be quite different. The general principles remain the same, with the use of surgery to control and treat infection and to define the anatomy of the fistula. However, patients with Crohn’s will be started on medication once the infection has resolved to try and heal the fistula. The surgeons at OneWelbeck will refer you to a gastroenterologist for comprehensive care.
Whichever treatment you have, if you smoke you should stop as this will promote healing.
