(Salt Lake City, UT)  –  Officials at the Hogle Zoo say a 19-year-old polar bear has died after her kidneys stopped working.  Rizzo the polar bear was euthanized at the zoo Saturday after veterinarians discovered her condition during a medical exam.  The zoo had placed the bear into an end-of-life monitoring program designed to make her more comfortable as the condition progressed.  Rizzo came to the zoo in 2012 as part of a commitment to conserving and protecting six specific wild animal species.Â