Whether kidney stones cause pain depends on whether the stones are moving within the kidney. If the stones are relatively large, they generally do not move within the kidney, and the patient will not feel pain. However, when the stones cause hydronephrosis (accumulation of water in the kidney), the patient may occasionally feel a slight swelling and discomfort in the lower back.

If the kidney stones are small, they are likely to move within the kidney, which can lead to severe lower back pain, clinically known as renal colic. This pain is quite severe, and it is necessary to go to the hospital for timely treatment.