After anal fistula surgery, the old gas is usually caused by intestinal dysfunction, anal sphincter relaxation, postoperative diet and other reasons. 1. Intestinal dysfunction: anal fistula surgery wound is large, if the amount of postoperative exercise is small plus the use of antibiotic drugs, will lead to intestinal dysfunction of the patient, more gas, diarrhea and other symptoms. 2. anal sphincter relaxation: after anal fistula surgery, the anal sphincter contraction weakness, anal sphincter relaxation will lead to the anus can not be closed, affecting the normal peristalsis of the stomach and intestines, leading to the symptoms of gas. 3. Postoperative diet is not appropriate: after surgery, the stomach and intestines will become fragile, if the patient eats more gas-producing food, it will lead to the symptoms of the patient’s non-stop exhaust. After anal fistula surgery is always ventilated, usually there may be surgical stimulation, dyspepsia and other causes, it is recommended that the patient go to the hospital for examination in a timely manner, under the guidance of the doctor to give symptomatic treatment.