Kidney stones are stone-like crystal formations made up of waste chemicals in the urine that have clumped together. There are 4 main types, those caused by urine infection, those made up of a combination of calcium and another chemical (usually oxalate or phosphate), those made up of uric acid crystals and those made up of cysteine. These stones form when there is an excess of the waste chemicals in the urine, and they can form in generally healthy individuals, however people with kidney disease or other illnesses have a higher risk. Having kidney stones however does itself put the patient at risk as they can cause kidney scarring or failure, or infection and even septicemia if the infection spreads to the blood stream. They are painful to pass, and if they do not pass naturally, may require surgery or lithotripsy to remove the stone completely. you are able to view a short informative video from NHS UK here
Calcium Oxalate kidney stone By GrammarFascist (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons
Can they be prevented?
Having a healthy balanced diet and drinking a lot of water can help prevent future kidney stones, but it is important to discuss any special circumstances about your individual medical condition with your doctor. Certain medications can also assist in kidney stone minimization.