The main causes of left lower abdominal pain are: 1. Colorectal tumor or inflammation. Patients may have pain and discomfort in the left lower abdomen, and patients with malignant tumors may be accompanied by low-grade fever, black stools, emaciation, and abnormal defecation. When the tumor is large, the swelling can be touched in the abdomen, and the diagnosis can be clear by combining with rectal palpation, abdominal CT, electronic colonoscopy and other examinations.2, urinary stones. Patients may have pain and discomfort in the left lower abdomen, which may be accompanied by hematuria as well as symptoms of bladder irritation such as urinary frequency, urinary urgency, urinary pain, and percussion pain in the renal area, which can be combined with ultrasound and CT examination of the urinary tract to make a clear diagnosis.3, gynecological diseases. Ectopic pregnancy, ovarian cyst torsion, ovarian tumors and other diseases can also appear in the left lower abdomen pain and discomfort, need to be further clarified.