Multiple kidney stones belong to a type of urinary stones. It is called multiple kidney stones when there are more than two stones within a single kidney. It may be caused by primary disease factors or secondary factors.1. Primary multiple kidney stones are caused by abnormal electrolyte metabolism in the body, resulting in over-saturation of some components in the urine and the formation of corresponding stones. It can be distributed within the renal pelvis or calyces, causing pain in the kidney area or urinary tract infections, hematuria, etc. 2. Secondary factors such as hyperparathyroidism lead to abnormal calcium and phosphorus metabolism in the body, which can lead to increased calcium content in the urine and can form multiple stones in the kidney. It can also be seen in congenital pelvic ureteral stenosis which leads to a large amount of water in the kidney, which over time can cause multiple kidney stones, smaller in size and larger in number, often due to obstructive factors.