Toby was taken to the vet the other day, and is doing much better. They are not sure exactly what was wrong with him, but they believe it might have been a severe case of a strain of "dog" flu. He has been put on anti-biotics as a precaution, and was also given anti-vomit meds. He has more energy now, and is walking around and greeting people as normal.
Much to our relief, the vet said his kidneys are functioning just fine, and we are awaiting the results of the other blood tests that were done. In any case, we are all very relieved to have our dog back. :)