a kidney donor的用法和样例：
- A kidney also takes urea and mineral salts out of the blood.
- Instead, they were told that Tessa had a kidney stone.
- Gender, age, delay between transplants, cumulative Thymoglobulin dose, and type of kidney donor were not associated with BK virus infection.
- NEWARK, N.J. - A judge has agreed to allow New Jersey's worst serial killer to donate a kidney, but the donor and his doctors have to meet conditions.