What are Kidney Stones?...

Kidney stones, also known as nephrolithiases, urolithiases or renal calculi, are crystals made out of dissolved minerals in urine found inside the kidneys or urinary tract.

Kidney stones typically leave the body in the urine stream; if they grow relatively large before passing (they're measured in millimeters) they cause severe pain most commonly felt in the flank, lower abdomen and groin.

Kidney stones are unrelated to gallstones.