Chester is 10 years old. Although they can live until 15-18 years of age, you need to take in the quality of his life. I may get some slack for this but here goes...does Chester seem happy? Does he greet you in any way? He no long has control of his bladder, able to eat solid foods. Now, he is very ill. How much longer will you be able to prolong his life until the next illness comes? It could just be that his body is tired. You've got lots to think about but you need to do what is best for Chester.
