It passes out of the body through a tube called the urethra. A kidney stone can develop when certain chemicals in your urine form crystals that stick together. The crystals may grow into a stone ranging in size from a grain of sand to a golf ball. Small stones can pass through the urinary system without causing problems. However, larger stones might block the flow of urine or irritate the lining of the urinary tract.
Most stones form in the kidney.
Some travel to the ureter or bladder. A smaller number are uric acid stones or cystine stones. One out of ten Canadians will have a kidney stone at some point in their life. Kidney stones occur much more commonly in men than in women. They tend to affect people in middle age, and occur more frequently hot climates.