To summarize the causes of postoperative fistula recurrence, there are seven common causes: 1. Failure to find a reliable internal port during surgery or incorrect treatment of the internal port, resulting in a false internal port, and even if an accurate internal port is found, the infected anal sinus, anal glands and their ducts are not completely removed, resulting in fistula recurrence. 2, the fistula is not yet formed when the surgery is urgent, easy to make the inflammation spread, the formation of new pus cavity and sinus tract, causing anal fistula recurrence. The fistula is bent during surgery, causing a false fistula or fistula to be left behind, or the necrotic tissue in the lean tract is not scraped clean, causing a recurrence of the lesion. 4, after fistula surgery, the wound is left with a foreign body, such as thread or cotton wool, which is buried by the surrounding granulation tissue, infection and affect the wound growth and healing. 5, anal fistula removal a sutured surgery, the application of intraoperative full-layer suture, do not leave gaps and dead space; suture tension should not be too large, suture tight, or make the healing delayed. 6, the surgery only removed the main fistula, leaving a part of the branch fistula, can cause postoperative anal fistula recurrence. 7, the patient is weak or accompanied by chronic diseases such as diabetes, tuberculosis, leukemia, anemia, etc., can also affect the wound infection and healing.