If men have long-term pain in the left lower abdomen, there are several possible reasons: 1, urinary stones, patients will feel pain and discomfort in the lower back in addition to pain in the left lower abdomen, and can do routine urinalysis, ultrasound of the urinary tract or CT examination to assist in the diagnosis.2, colorectal cancer, including colon cancer and rectal cancer. Patients will feel vague pain in the left lower abdomen, and often accompanied by diarrhea, blood in stool, or even thinning of stool and a sense of urgency and heaviness, and should improve the examination of tumor markers as well as colonoscopy to assist in diagnosis. 3. colitis, manifested as vague pain in the left lower abdomen, and often blood in stool, and should improve colonoscopy to make a clear diagnosis.