A fistula means a fistula, and is more likely to occur around the anus, or anal fistula. It can also occur in the abdominal cavity, for example, when a tumor of the intestine is prolonged, which can lead to the formation of a fistula between the intestine and the intestine, or between the intestine and the stomach, also known as a fistula. An anal fistula is formed when a paranal abscess becomes infected and breaks down on its surface. It has an internal opening inside the anus, in the anal canal, or in the rectum, and passes through the fistula around the anus and then passes from the external opening to the subcutaneous area, where fecal fluid flows from the inside of the fistula with a foul odor. After the diagnosis of anal fistula is clear, surgical excision or fistula stitching is required. If an intra-abdominal tumor has formed an internal fistula over time, it also needs to be removed surgically.