_:vb50956636 . _:vb50956636 . _:vb50956636 "A urinary system disease that is located_in the lower urinary tract and is characterized by the formation of a stone."^^ . _:vb50956636 . _:vb50956636 . _:vb50956636 "url:http://en.wikipedia.org/wiki/Calculus_%28medicine%29"^^ . _:vb50956636 .