Hidden pain in the left side of the stomach may be caused by gastrointestinal diseases, urinary system diseases, gynecological diseases, spleen diseases and so on. 1. Gastrointestinal diseases: such as chronic gastritis, gastric ulcer, ulcerative colitis, sigmoiditis, proctitis, irritable bowel syndrome, colon cancer and so on can lead to the left abdominal pain. 2. Urological diseases: such as left kidney stone, left ureteral stone, left renal cyst, etc., can also lead to vague pain in the left abdomen. 3. Gynecological diseases: such as left ovarian cyst torsion, left salpingitis, etc., can also lead to vague pain in the left abdomen. 4. Spleen diseases: such as splenic cysts, splenic abscess, splenic infarction, etc., can also lead to vague pain in the left abdomen. There are many other causes of left abdominal pain, which should be taken seriously, and it is recommended that the patient should consult a doctor in time to find out the cause of the disease and follow the doctor’s instructions for further treatment or therapy.