There are various reasons for the vague pain in the left abdomen: 1. It may be rectal or sigmoid lesions, which can cause erosion of the intestinal mucosa, or even polyps and malignant tumors inside the intestine, which can lead to pain in the left side of the abdomen. 2. It may be an infection of the urinary system, which not only causes vague pain in the left side of the abdomen, but also causes frequent and urgent urination, and even blood in the urine. 3. The symptoms of chronic cervicitis will not only lead to vague pain on the left side of the abdomen, but also cause excessive leucorrhea, irregular menstruation and abdominal pain during menstruation. 4. Left abdominal pain may occur due to left ureteral calculi, which may also be accompanied by painful urination. You can go to the hospital to improve the routine urine examination and abdominal ultrasound, as well as to do intestinal examination to confirm the disease.