A hard vertical strip in the anus is first considered to be an anal fistula, which is the sequelae of a perianal abscess that has broken down or has been surgically incised and drained. There is an external opening around the anus, which is granulomatous and repeatedly drains pus, and an internal opening in the anal fossa, with a hard strip of fistula between the internal and external openings. If the fistula can be palpated by finger palpation, the leak is a low anal fistula, and most of them can be treated clinically by fistulotomy or fistulotomy. In contrast, high anal fistulas may lead to postoperative anal incontinence if a one-time incision or excision is performed, so most high anal fistulas are threaded. It is important to note that all anal fistulas should be treated surgically in order to be cured, so once the diagnosis of anal fistula is clear, the patient should be treated surgically in time. The actual fistulas can be a lot more difficult to treat because they are simple and complicated.