The common causes of left-sided abdominal pain include inflammation or tumor of the digestive system, acute pancreatitis, ectopic pregnancy, ureteral stone, etc., which should be consulted in time, and the relevant examination should be completed to clarify the cause. 1. Inflammation or tumor of digestive system: colitis, colorectal cancer, etc. can cause left-sided abdominal pain, which may be accompanied by changes in stool characteristics. 2. Acute pancreatitis: mostly due to inflammatory injury caused by cholelithiasis and biliary tract infection, etc., patients may have the symptom of pain in the left upper abdomen, which is mostly persistent and severe pain, and may radiate to the back and the whole abdomen, and it may occur suddenly after having a full meal and drinking alcohol, and the pain may be relieved when leaning forward, which can be accompanied by nausea, vomiting and fever. 3. Ectopic pregnancy: refers to the fertilization of the egg outside the uterine cavity due to reproductive system diseases or injuries, often manifested as a hidden pain or soreness in one side of the abdomen, accompanied by menopause, vaginal bleeding, and in severe cases, can lead to fainting and shock. 4. Ureteral stones: mainly caused by metabolic abnormalities, urinary tract infections, obstruction or foreign bodies, etc. When ureteral stones attack on the left side, severe abdominal pain can occur, and some patients may also be accompanied by nausea, vomiting, urinary frequency, hematuria, urinary pain and other manifestations. In addition, ovarian cysts, kidney stones, digestive disorders can also lead to symptoms of left-sided abdominal pain, but this symptom alone is not enough to diagnose the disease, it is recommended that the body is not feeling well in a timely manner, to identify the cause of the disease, and if necessary, targeted treatment.