Old diarrhea is also known as diarrhea, diarrhea may be a stomach problem or intestinal problems, or caused by other diseases. There are many reasons for diarrhea, which can be induced by intestinal diseases, such as inflammatory bowel disease, bacillary dysentery, cholera, colorectal cancer, irritable bowel syndrome, etc.; gastric diseases, such as chronic atrophic gastritis, gastric resection, etc.; and there are also problems with both the stomach and the intestines, such as acute gastroenteritis, gastrointestinal disorders. In addition to the above reasons, diarrhea may also be caused by other diseases such as hyperthyroidism and anaphylactic purpura. Therefore, diarrhea may be caused by stomach problems or intestinal problems, or other diseases. It is recommended to go to the hospital when you have constant diarrhea and ask the doctor to make a judgment and clarify the cause.