The photograph shows bivalved right and left kidneys. Diet plays a part in stone formation. Some cases are hereditary.
Some cases are due to inborn errors of metabolism such as gout and cystinuria.
There are four main types of stones - calcium oxalate, uric acid, struvite and cystine. Annual incidence of 7 to 21 cases per 10,000 persons in the United States. Males are affected more often than females. Peak age of onset between 20 to 30 years. Uroliths vary considerably in size, shape and color and are not particularly revealing as to their chemical content.