Patients with urinary tract stones are usually instructed, first of all, to drink a lot of water and urinate a lot, which is the basis for stone removal. Doctors also often advise patients to change their position, such as head down and feet up, why is this? It starts with the structure of the urinary ducts within the kidneys, where the kidneys produce urine through intrarenal ducts connected to the main urinary ducts. The intrarenal urinary duct is somewhat similar to a building in that it is a three-dimensional duct system with different rooms connected by corridors and then connected to an elevator. As shown in the picture, when standing, the renal ducts are also divided into different floors, but the elevator only has entrances and exits at the middle floor, so to take the elevator down everyone can only walk from above or below to the middle floor. Most urinary stones contain calcium and are denser than urine, so they sink to the bottom in the urine. Small stones or small pieces after lithotripsy usually sink in the lower pipes and have difficulty as they need to climb the slope to enter the main duct to drain out. At this time, if you change the position, such as head down and feet up, the tube below the kidney will become the tube above, and because of gravity, the stone will naturally descend to the middle part and go down in the elevator. However, this condition should be careful to act according to the physical condition, especially for the elderly, to avoid unnecessary damage caused by over-activity.