Kidney stones consist of the collection of certain substances from the urine and the formation of crystals. These crystals are of different types according to their constituent material, but most of them originate from the accumulation of calcium, such as calcium phosphate and others.

Most of the time, these stones are thrown without feeling them, but they may stick to the wall of the urinary system and crystals gather around them, which leads to their large size and difficulty in expelling them on their own.