My 12 year old dog has cancer, and has started drinking a large amount of water. Does anyone know the reason?

Princess is a 12 year old Australian shepherd/Akita, the best dog you could ever imagine! She isn't just a family pet she is a family member. She is my Dad's dogs puppy and I watched her be born. I know people say that their dog is like their baby, but she really is. I don't know how i'm going to deal with this, I've always said that I will not let her suffer, she already has to be on pain medication because she has hip dysplasia. We took her to the ER last weekend and then her regular vet yesterday, and her vet said it has spread to her lungs and there is nothing they can do. She has had to have a mastectomy already (3 years ago) and luckily it was benign then. I'm going to call the vet soon but I was hoping someone would know the answer to my question. She is drinking water like crazy she will drink a whole gallon at a time if I leave it down for her. Yesterday she drank so much so fast that she puked it all up, on an empty stomach. Has anyone gone through this with their dogs that have had cancer?I called the vet and they are going to put her on some anti nausea medication and extend the antibiotic she is on now. They said it could be possible she is vomiting because she is drinking too much water and is causing her to get nauseated and the reason she is drinking so much could be because trying to make up for the food that she is not eating too much of. Thank you everyone it means a lot

Only a Vet can diagnose, but my GUESS is that she is in Renal/Kidney Failure. You've said that you will not let her suffer, so don't.

Ask vet to do a diabetes test on her. This causes excessive thirst.So sorry about the cancer.

Her liver may be failing. And yes I have. I currently have a 13 year old foster dog who drinks excessively because her liver are a lil' bit faulty. She does not have cancer altho she did have tumors on certain parts of her body that were removed not too long ago & haven't grown back. Please bring her to another Vet for a 2nd opinion. A blood test should be done to check if her liver is still functioning alright or not.Hope this helps.

Yes I had a GSD who died of cancer aged only 7 and that is very rare in this breed, I only have GSD's and JR's and one of them died with lung cancer. Your lovely dog should be put to sleep and don't cry until she's passed over and be proud that she had a great family to love her, there's so much cruelty in this world and your dog was never part of that. She's drinking because her kidneys are failing and Diabetes has set in so she's really suffering, you will meet her again I promise you that as we must have faith.Please read this link.http://www.petloss.com/rainbowbridge.htm

I'm really sorry about this but once cancer has spread to the lungs, you really do have to face the fact that she doesn't have very much longer of good quality life. At 12 she's had a long innings already and I'm afraid now is the time you must put your own, understandable, feelings aside and after discussing the situation with your vet, who if he can, will offer treatment help her help her with her suffering. We have been there, too often, and will never do lingering when it's not necessary for our beloved pets.I'd suggest that drinking lots is probably all part of the process when the system starts to fail. So sorry.