Some people can carry kidney stones for a long time without any symptom.
Kidney stones range in size from a fraction of an inch to several inches. Usually small stones like less than 1/5 inch or about 5 mm in size usually can pass through the urinary tract and out of the body on their own with little or no pain. You just need to drink plenty of water.
Larger stones, 2/10 inch or 8 mm to 1/5 inch or 1 cm can be quite painful, though. If you feel pain, you'll get medical help to pass them out.
Fortunately kidney stones generally don't cause permanent damage.