I think my sisters dog has cancer / is dying dogs

My sister moved to Germany and I took in her dog. I have my own elderly dog (11 years old) and her dog is around 13 years old. He stopped eating the last few days and I thought he was just being weird. I don't monitor their food intake, I just feed them in the morning and they graze all day. Both are at target weight.

Yesterday I barely got him to eat canned dog food (highly unusual). Today I've tried offering him Tuna and then a bite of everything in the refrigerator. I've been getting him to drink by basically forcing him to drink. I let the dogs train me to ask for a treat during the day, so I think this is the third day he hasn't had an appetite.

He is old and doesn't appear to be in pain so I don't think he is going to spring back from this one. I'm taking him to the vet in 15 minutes. Not excited about breaking the news to my sister. I talked to her yesterday (she is an DON/RN), and she told me to keep an eye on him today and take him in if he didn't improve/was vomiting.

I think I made it pretty clear that I thought he was going to be passing :/

If he has cancer or a serious disease and doesn't have much time left, should I put him down? I can't ask my sister since the time difference. I think she would be onboard with ending it before it got too painful

Submitted December 29, 2014 at 11:33PM by cHJvZ3JhbW1lcg http://www.reddit.com/r/dogs/comments/2qq9f1/i_think_my_sisters_dog_has_cancer_is_dying/ dogs