Kidney stones (also known as renal calculi, nephrolithiasis, or urolithiasis) are small, hard deposits of minerals and acid salts that form inside the kidneys. This is a common condition that affects approximately 20% of the population.
Kidney stones form when the components of urine (fluid and various minerals and acids) are out of balance. Some examples of common types of stones include calcium, struvite, uric acid, and cystine. When urine is more concentrated (e.g. not drinking enough fluids), these minerals and acids crystallize and eventually grow bigger to become a kidney stone. Other less common causes include inherited metabolic disorders, kidney diseases, gout, inflammatory bowel disease, and certain drugs.
However, it is common for kidney stones to have no definite single cause. A number of factors, often in combination, create the ideal condition for kidney stones to develop in susceptible people.