The constant pain in the left kidney may be caused with urinary stones, pyelonephritis, left kidney cyst, etc. Differential diagnosis is needed. 1. Urologic stones: for example, left kidney stones, the movement of stones in the kidney can continuously damage the mucous membrane and cause pain. 2. Pyelonephritis: the left kidney is stimulated by inflammatory factors, which can cause constant pain in the left kidney. 3. Left kidney cyst: larger kidney cysts can compress the renal parenchyma and surrounding tissues, which can cause pain in the left kidney. There are many other causes of left kidney pain, such as renal vein thrombosis, etc. It is recommended that people with left kidney pain go to regular hospitals in a timely manner, to clarify the cause of the disease, and standardized treatment under the guidance of the doctor.