In September, Rex presented his housemate, Peaches, with the gift that keeps on giving -- a desperately needed kidney. Today, the 6-year-old Labrador retriever and 8-year-old English bulldog from Seattle are doing well after their surgeries, performed at the UC Davis Veterinary Medical Teaching Hospital. This was the first successful clinical kidney transplant between unrelated dogs using a new combination of immunosuppressive drugs, given to Peaches to prevent her body from rejecting Rex's donated kidney, according to Dr. Clare R. Gregory, who performed the surgery. Prior to this, only dogs with access to the kidney of a relative could receive a donated kidney at UC Davis. Because of the genetic diversity developed during centuries of breeding, dogs are considered the most difficult species in which to perform transplants of organs from unrelated donors, Gregory says. When owners Marty and Joanne Modance brought their dogs to UC Davis, Gregory had performed six experimental kidney transplants between unrelated dogs using the new drug combination. Peaches provided an opportunity to test the new drug combination clinically -- on a veterinary patient rather than a research animal.