I don't want to give false hope, because this might be something completely different, but I thought I'd share, just in case.
Two years ago Blaze (who was 14) dropped half his weight in a month. He would eat, but nothing was getting absorbed. His stool was the colour of wheat and was barely solid, almost like pudding. It was also extrememly acidic and burnt his butt hairs away.
We did every type of test we could, but nothing was so far out of wack to explain it. The X Ray showed that he didn't have a liver. It was gone. There was nothing else wrong that we could see
Now at his age, we were given the option of the MRI to look closer, but there was no way I was going to put him through surgery at 14, and the cost of the MRI would have used up all of my funds. I talked it over with the vet and we decided to just treat him for the no liver and overworked pancreas issue.
He gets 1 tsp. of pancrease-v powder on his food and half a flagyl pill everyday. The powder has to sit on everything he eats for twenty minutes. If he feels frisky and eats the garbage or anything without the powder, he feels it for the next three days.
He is a healthy weight now, and the stool is pretty normal most of the time. We did an X Ray not too long ago, after her had his first and knock on wood only seizure, still no liver visible, but again, we haven't opted for the MRI.
I hope everything works out for you and your pup.