What causes the pain of kidney stones?
For the most part, a kidney stone does not cause pain while it is located in the kidney where it was formed. When a kidney stone becomes dislodged and falls into the ureter (the tube which drains the urine from the kidney down to the bladder) the person feels pain. The pain is due to the obstruction of urine flow caused by the kidney stone blocking off the ureter. The pain is actually due to back pressure of urine in the affected kidney.