Kidney stones are one of the most common and most painful medical problems known.
They occur when salts in the urine precipitate and form solid material. Stones can vary in size from as small as a grain of rice to as large as an apple. The pain of passing a kidney stone is said to be one of the most severe pains which it is possible to experience Small stones can cause pain as they pass from the kidneys down to the bladder and then to the outside, because their sharp edges tear at the lining of the urinary tract. Large stones can get stuck in the kidney or in the bladder. Then they have to be removed, as they can cause blockage of the flow of urine, pain, infection and kidney damage.