There are many diseases that cause hidden pain in the left side of the abdomen, which may be intestinal diseases, digestive system diseases, urinary system diseases, gynecological diseases and so on. 1. Intestinal diseases: sigmoid ulcerative colitis can cause symptoms of left-sided abdominal pain, which can be accompanied by diarrhea, mucous pus and blood stools. 2. Gastritis, gastric ulcer due to inflammation of the stimulus, can cause hidden pain in the left side of the abdomen accompanied by acid reflux, nausea, abdominal distension symptoms. 3. Urological diseases: left-sided ureteritis, acute cystitis can cause symptoms of left-sided abdominal pain, accompanied by frequent urination, urination pain and other symptoms. 4. Gynecological diseases: female pelvic inflammatory disease, ovarian cysts can cause hidden pain in the left side of the abdomen can be accompanied by abnormal vaginal discharge and other symptoms. In the life of the left abdominal pain symptoms, to go to the hospital in time to do the relevant examination, active treatment; do not take oral medication, so as not to delay the condition.