A stone in the left kidney can be diagnosed as a kidney stone, which is a disease of the urinary tract. Possible causes: 1. Drinking less water, the urine is overly concentrated, so the solute is gradually precipitated. This statement is currently the most common in clinical practice and is called the supersaturation theory. Mostly, the amount of fluid supplemented by the patient is insufficient, the evaporation is excessive, and the formed components in the urine form crystals and precipitate, gradually forming stones. The first deposits are made on the papillae of the kidney, forming kidney crystals, which act as nodules for the stones, similar to sedimentary rocks, and grow larger and larger, forming stone-like changes. After increasing in size to a certain extent, they fall into the renal pelvis or calyces, forming stones in the kidney, and kidney stones drain into the ureter and bladder, forming stones in the ureter and bladder.2. Kidney stones caused by metabolic abnormalities, such as hyperuricemia can form uric acid crystals, uric acid stones, etc.; abnormal calcium and phosphorus metabolism in patients with secondary hyperparathyroidism or primary hyperparathyroidism can also form multiple stones in the kidney.