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SACRAMENTO–

The Sacramento Zoo’s senior Sumatran Tiger will undergo surgery to treat kidney stones.

Castro the tiger is no stranger to medical attention. The 15-year-old carnivore suffers from lymphoma, a cancer that is fatal, but his condition has improved with chemotherapy.

The procedure scheduled for Tuesday will insert tubes so that urine can be drained from his kidneys to his bladder. Human doctors, as well as veterinarians, will take part in the elaborate procedure.

Castro has been a mainstay of the zoo’s big cat captive breeding program. He has sired five cubs, including one last March.

While Castro’s breeding days are over and he is reaching the limit of his life expectancy, zoo officials say they are committed to making his life as comfortable as possible.

There are only about 500 Sumatran Tigers in the wild and just 200 in captivity.