Your surgeon may use a special telescope with a light on the end called a proctoscope to see inside your rectum. He/She may also use a fistula probe. This is a tiny instrument that will be inserted through the fistula. Your surgeon may perform these examinations under general anaesthesia. This means you will be asleep during the procedure. You may be asked to have an ultrasound, CT or MRI scan to help find out how the fistula is linked to your sphincter muscles.
Attribution: BUPA