After cholecystectomy, the third day of black stool may be caused by normal physiological phenomenon, upper gastrointestinal bleeding and other reasons. 1. Normal physiological phenomenon: usually after cholecystectomy, the patient’s body is relatively weak. If the patient ate pig’s blood or duck’s blood in the first two days after the operation, the stool may turn black on the third day of defecation. If the patient has no discomfort, no special treatment is needed. 2. Upper gastrointestinal bleeding: generally after cholecystectomy, the black color of the stool on the third day is usually not directly related to cholecystectomy. It may be the patient’s upper gastrointestinal bleeding, the patient’s clinical manifestations after the onset of vomiting blood and black stool, so the patient’s stool color may be black. When the bleeding is severe, the patient may also have symptoms of anemia. There are many other reasons for black stool on the third day after cholecystectomy, and patients are advised to actively seek medical attention to avoid delaying their condition.