A vague pain in the left lower abdomen is usually the result of colitis, diverticulitis, and pelvic inflammatory disease. 1. Colitis: Since the left lower abdomen is mainly colon, if the diet is not proper and colitis occurs, there may be vague pain in the left lower abdomen, and there may be diarrhea and other symptoms. 2. Diverticulitis: Inflammation of the diverticulum may cause abdominal pain and bloating, resulting in inflammation of the diverticulum and surrounding mucosa, leading to vague pain in the left lower abdomen. 3. Pelvic inflammatory disease: Pelvic inflammatory disease includes inflammation of the uterus, fallopian tube and pelvic connective tissue inflammation. If there is fluid and pus accumulation in the fallopian tube, there may be vague pain in the left side of the lower abdomen. There are many causes of pain in the left lower abdomen, if you have pain in the left lower abdomen, you should go to the hospital in time to find the cause of the disease and follow the doctor’s instructions for treatment.