Caused by the left side of the stomach pain has many reasons, the patient should go to the hospital line in a timely manner to carry out a formal examination, clear causes, line corresponding treatment. Causes of abdominal pain on the left side of the causes, common are the following aspects: 1, ulcerative colitis, the cause is not clear, may be related to genetic, environmental, immune and infectious factors, the main manifestation of the left lower abdominal pain, diarrhea, mucus pus and blood stools, which can be accompanied by fever, night sweats, general malaise, etc. 2, ureteral stones, ureteral stones can be seen on the left side of the renal colic, hematuria, usually the pain of stones, more intense, pain can radiate to the thighs or the vulva. 3, ureteral stones, ureteral stones can appear left side of the renal colic, hematuria, usually stones The pain can radiate to the root of the thigh or the perineum. 3, there is also a urinary tract inflammation, infection caused by women may appear in the fallopian tube or ovary inflammation, manifested in the left side of the abdominal pain, menstrual disorders, infertility, the gradual spread of the pathogen to the uterine cervix, the endometrium, is a common pathway of infection, may be related to the patient’s poor hygiene habits, menstrual sex, and the body’s weakened resistance ability. 4, there is also colitis, colon cancer, manifested as abdominal pain, abdominal mass, defecation habits, and stool shape change, advanced patients can appear emaciation, anemia, malignant fluid, distant organs metastasis. Therefore, there are many causes of left sided hidden pain, must be related to the examination, for the cause of the targeted treatment.