Female left side lumbar swelling can be caused by the following causes: first, lumbar muscle strain, lumbar muscle strain can have symptoms of lumbar muscle swelling, often due to long-term work and work with one side of the waist, resulting in chronic muscle damage, then early examination and examination to exclude other diseases to diagnose; second, tumor in the muscle, when the left side of the lumbar muscle tumor, can have the left side of the lumbar swelling symptoms, can be accompanied by pain; third, kidney disease, when the left side of the kidney has inflammation or tumor, can have the left side of the lumbar swelling Thirdly, kidney disease, when there is inflammation or tumor in the left side of the kidney, there can be symptoms of lumbar soreness and swelling, which can be accompanied by hematuria and proteinuria, then we should check the ultrasound, CT and routine urine tests of the kidney for diagnosis and early treatment.