Kidney stones

Kidney stones are stones that form in the kidney or the bladder; they are known by doctors as 'urinary calculi'. Kidney stones can vary in size from tiny microscopic fragments to huge stones that fill up much of the kidney. It is a relatively common condition and may affect up to one per cent of adults in Western countries. Men are affected about four times more frequently than women.
What causes kidney stones and who is at risk?

The kidneys filter blood and the fluid produced is concentrated and drains out of the kidney as urine into the bladder. Urine contains various substances called 'salts' (eg calcium salts), which can potentially form stones if they become too concentrated. Urine also contains substances that inhibit the formation of stones.