Pain caused by kidney stones is generally in the lumbar region, that is, below the rib cage and beside the spine. If the stones are relatively small, most do not cause discomfort; however, when small stones fall into the ureter, they can cause renal colic. If the stones are large, they can cause kidney swelling or even infection, leading to a sour distention and pain in the lumbar area. The pain generally occurs on the side where the stone is located. In such cases, it is necessary to visit the hospital's urology department promptly for an ultrasound, and possibly a CT scan, to clearly determine the specific location and size of the stones, and whether there is associated swelling or infection, in order to manage the condition appropriately.