These are relatively unusual problems whereby there is a communication between the inside of the back passage and the skin. They are most often
related to an infection just inside the back passage which tracks onto the skin, but occasionally it can be related to other conditions of the bowel such
as Crohns disease (one of the inflammatory bowel diseases).

What symptoms do they cause?
Some fistulas present acutely with an abscess near to the back passage which often will require drainage as an emergency with an operation. Other
fistulas appear more gradually and may give a pattern of intermittent swelling close to the back passage with discomfort, followed by discharge of pus
and blood for a few days before the pattern repeats.

What treatment do I need?
Fistulas can be simple, but some are much more complicated. Depending on the appearances and history in clinic, an MRI scan may be helpful
in showing the exact anatomy of the fistula to help with planning surgery. Simple fistulas can usually be managed with a single day case operation,
performed under general or spinal anaesthetic, where the fistula is laid open to the air and allowed to heal by scarring from the inside out which
usually takes a few weeks. More complex fistulas cannot be managed like this, usually because the fistula crosses too much of the sphincter muscle, in
which case laying it open would risk problems with incontinence. Instead, these fistulas are often managed over a longer period, sometimes involving
multiple procedures, but usually the first procedure is to place a stitch into the fistula (called a seton) which keeps the fistula open at both ends, thus
removing the risk that the fistula could result in an acute abscess.