If you have symptoms that suggest an anal fistula, your healthcare provider may refer you to a specialist who specializes in colon and rectal diseases. The specialist will ask about your symptoms and your medical history. During your physical exam, the doctor will look for a fistula opening near your anal opening. He or she may press on the area to see if it is sore and if pus comes out. Different methods may be used to help with the diagnosis, such as a fistula probe, an anoscope etc.
The doctor may also use imaging studies such as an ultrasound, which creates an image of the anal area using sound waves. Or they may include an MRI, which makes images of the area by using special magnets and a computer.