Is pig kidney suitable for humans?

The transplantation of organs from one species to another introduces a ques tion of compatibility not seen in allotransplantation, the ability of a kid ney to perform its physiological function in the new host environment. It h as been assumed that an allotransplanted organ will function normally if is not rejected; ample experience supports this assumption. This luxury will not exist in the field of xenotransplantation, where the issues of comparat ive physiology will assume great importance. From many standpoints, the pig kidney seems an ideal donor for xenotransplantation. They are of similar s ize and have remarkably similar internal anatomy. Even if the immunological problems could be overcome, there is almost no direct experimental evidenc e to answer the question of whether or not a pig kidney can function in a h uman body.