Hidden pain in the left upper abdomen is commonly caused by pancreatic diseases, gastric ulcer, gastritis, digestive tract tumors and so on. 1. Pancreatic diseases: Chronic pancreatitis can manifest as persistent pain in the upper left abdomen, accompanied by abdominal pressure or burning sensation. Disease progression to the advanced stage can be accompanied by abdominal distension and diarrhea, fatigue, emaciation and other symptoms. 2. Gastric ulcer and gastritis: Gastric ulcer and gastritis are one of the most common causes of upper left abdominal pain. Gastritis can be manifested as a vague pain in the upper abdomen, which can be accompanied by abdominal distension, acid reflux, loss of appetite, nausea and vomiting and other symptoms. Gastric ulcer abdominal pain is often accompanied by regularity, often manifested as pain half an hour after meals. 3. Tumor of digestive tract: pancreatic tumor, stomach tumor, intestinal tumor can lead to hidden pain in the upper left abdomen because of the compression of the tumor. There may be other reasons for the pain in the left upper abdomen, so it is recommended to go to the hospital in time to improve the examination and give targeted treatment after clarifying the cause of the disease.