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.