Occasionally, mineral deposits form in the kidneys – typically, when there are high levels of calcium (or oxalate or uric acid) in the kidneys and/or not enough water in the kidneys to dissolve wastes. These undissolved wastes leave deposits in the kidneys, which then form crystals and kidney stones.
Kidney stones can often pass naturally. Some cases, however, may require other procedures to break up or remove stones, including lithotripsy, a procedure that uses shock waves to break the stone into passable pieces.
There are also a number of varieties of cancer that affect the kidneys – the most common of which is called renal cell carcinoma. Early detection of this form of cancer is important – and can result in a successful surgery that removes only the cancerous part of the kidney instead of the entire kidney.