Kidney stones (nephrolithiasis) are deposits inside the renal or urinary tracts, the latter are also called urinary stones. They develop when the solubility product of specific salts in the urine is exceeded. Other names are nephrolith (greek nephros = kidney, lithos = stone), kidney concrement, or renal calcification. Kidney stones primarily arise in times of increased need of liquid, e.g. during summer. Kidney stones can form inside the renal pelvis, but there can also be crystalization the renal tissue, e.g. in case of an urate kidney. Kidney stones can impair the function of the kidney, they can lead the renal dysfunction. The urine accumulation caused by such a stone is very painful.