How long to take a kidney stone to pass?

Kidney stones are abnormal, hard, chemical deposits that form inside the kidneys. They are often as small as grains of sand, and pass out of the body in urine without causing discomfort. However, the deposits can be too big to be flushed from the kidney. Kidney stones that travel into the ureter can get trapped, causing significant pain. A stone in the ureter may not pass on its own and need to be removed. How long it may take to pass out of the ureter is highly variable. Or, it may not pass on its own and need specific treatment.