The pain in the lower left back and often want to go to the toilet may be caused by urinary tract infection, urinary stones and other reasons. 1. Urinary tract infection: such as pyelonephritis, can appear frequent urination, urinary urgency, urinary pain and other symptoms, serious patients can also be accompanied by the symptoms of pain in the lower left back. 2. Urinary stones: such as the left side of the ureter, urethra and other parts of the stone, there can be a phenomenon of pain in the lower back and abdomen, can be accompanied by a strong sense of urinary tract irritation, which can lead to often want to go to the toilet. It is recommended that the left lower back pain and often want to go to the bathroom in a timely manner to the hospital, a clear cause, under the guidance of the doctor for standardized treatment, so as to avoid delays in the condition of the body to bring adverse effects.