your dog is in a terminal stage of cancer where the weight loss is a condition known as cachexia. The blood work may show anemia and a drop in platlets.

You may wish to ask your Vet for the antibiotic Doxycycline. One of the main problems that may occur is secondary infection by bacteria due to a suppressed immune system. Opportunistics infections can become serious quickly. The Doxycycline is a wide spectrum antibiotic, and has some minor anti-infammatory properties. At this stage there is no reason not to give antibiotics as a preventative.

It's always a good sign the appetite is still there. A good opportunity for you to pamper your puppy with whatever it wishes to eat. You might consider addiing fish oil to the diet. Try 2000-4000 mg per day (for a large breed dog). The Omega-3s in the fish oil are ant-iinflammatory, and might help with any lactic acid imbalances. Besides most dogs will relish the taste of the fish oil- yummy. Speak with your Vet about administering Prednisone. It could make the puppy wee wee problem worse, but will make the dog feel more comfortable, especially one with arthritis. Also discuss with your Vet the possibility of administering low doses of Torbutrol (a doggy narcotic) to relieve any possible pain, if puppy seems restless. Doses as low as 2.5 mg can be effective. The less the better due to the sedating effect. It still puzzles me why it isn't precribed the first night after neutering or spaying, but that's another subject.