Old dog lost 3 kg in 2 weeks.

The dog was treated by Dr V on May 1, 2012 for coughing. The cough had disappeared after 3 days of drugs and the dog stopped eating. Blood test was taken but he said that he was not told of the results. I apologised to him and reviewed his records. Liver enzymes were high and Dr V had prescribed heart medication and advised review in 14 days . However, he did not turn up and now it is May 24, 2012 and the dog is very thin and weak. A loss of 3 kg from May 1 to May 24 is too drastic.   

Now it is very thin. The 62-year-old man came with his daughter. As he had white hair, I said incorrectly that his grand-daughter was accompanying him. I asked Dr Daniel to handle this case with me. Respiratory rate and pulse were normal.

SIGNIFICANT FINDINGS 
1. Below normal rectal temp at 37.5
2. Weight loss
3. No appetite and does not drink water.
4. Periodontitis Stage 4 and painful throat area.
5. No abdominal pain or swelling of the liver which is good news.
6. Penile sheath was swollen.
7. Heart murmurs.
"This dog could be more than 15 years old," the father said. He remembered I did a tail amputation on a tail lump in 2007. "He had seizures in 2010," I saw the record but he could not remember. His daughter confirmed and said no more seizures.

What's the cause of this loss of appetite and painful throat? Blood test, urine test and IV drip done first.