There's a lot of interesting graph theory there. Check out more about kidney matching here: <a href="http://blog.sciencenews.org/mathtrek/2007/08/kidney_matchmaking.html" rel="nofollow">http://blog.sciencenews.org/mathtrek/2007/08/kidney_matchmak...</a><p>If anyone is really interested in this kind of stuff, shoot me an email. I'm working on a couple research projects in this area.