In the early stages of the disease, the pus is more frequent, yellowish in color, sticky, and has a heavy fecal odor. As the disease progresses, the pus gradually decreases, sometimes not, and is as thin as water. If the patient is overly tired, the pus increases and fecal matter may be present. Sometimes the fistula can be closed temporarily, but soon the patient will develop fever and localized swelling and pain. If the closed opening breaks down again, the symptoms gradually disappear after the pus flows out. Common clinical symptoms: 1. Itching. Pus constantly irritates the perianal skin, resulting in anal dampness and itching. 2. Pain. If pus accumulates and does not drain well, swelling and pain will occur. 3. Pus flow. If the pus accumulates to a certain level, the fistula breaks down and pus flows out. 4, poor defecation. A fistula that does not heal for a long time can cause a fibrotic scar to form around the anorectum, causing difficulty in defecating.