Undigested leaves in stool, i.e., undigested food in stool, there may be two possible causes, physiological causes include eating too fast, food ingredients are not easy to digest, etc.; pathologic causes include short bowel syndrome, chronic pancreatitis, inflammatory bowel disease, etc. 1. Physiological reasons: eating too fast without sufficient chewing in the mouth, or eating food rich in fiber, protein and other indigestible ingredients, may lead to undigested food in the stool. 2. Pathological reasons: for example, patients with short bowel syndrome have shorter intestinal tract than normal people, the time for digestion and absorption of food through intestines is not enough, and part of the food is discharged through feces without being fully absorbed by intestines; patients with chronic pancreatitis have impaired exocrine function of pancreas, and pancreatic secretion of pancreatic juice is not enough to fully digest food which can lead to the appearance of undigested food in feces; patients with inflammatory bowel disease have impaired intestinal mucosa, and the absorption function of intestinal tract is destroyed, which can also lead to the appearance of undigested food in feces. In inflammatory bowel disease, the intestinal mucosa is damaged and the absorption function of the intestines is disrupted, which can also result in the expulsion of undigested food. If there is undigested food in the feces repeatedly, it is recommended to go to the hospital in time, under the guidance of professional doctors to clarify the cause of the disease, so as to avoid delaying the condition.