Kidneys were organs present in humanoid species. After House murdered the Time Lord known as the Corsair, his kidneys were given to Uncle, one of House's patchwork slaves. (TV: The Doctor's Wife)
When the Doctor's TARDIS matrix was transported into the body of Idris, her energy was burning out the body where she had been placed. As one of the first signs, she stated that one kidney had already given out. (TV: The Doctor's Wife)
