Please join this yahoo group:
DogLiverDisease : Dog Liver Disease
The members there are very helpful and there are a number of different breeds there as well that also have liver shunts.
The RC kibble is the correct food. You can also use Hill l/d (wet) food, which has more moisture content. You may need to add some water the RC kibble if he is having urine issues. Did they check for stones or crystals in his urine?
What was his Bile Acid results?