Older kitty not doing well

Question
Dear Norman
my Buddy is 16 years old. He has consistently been getting thinner and thinner over the past year.
I took him to the vet as he breaks out in sores around his chin and head every now and then (its not fleas) and we decided to do some tests as he was very thin at the time.
The vet thought that he may have a kidney disease or dis-function as he was very skinny and drank quite a bit of water. Well, we did a full blood work up, kidney function test and kitty Aids tests.
The kidneys are fine and there is no viral infection but the blood work indicted that there is something wrong with his red and white blood count.
As the next step would be to have a bone marrow test done, which is very expensive and uncomfortable, i believe for the kitty, I would like to know if you think that if Buddy has a bone or blood cancer that there would be any way to save him or if I should rather make him as comfortable in his last days/months and let him go.
His appetite is still very poor, and it seems as if he his pain when eating. Chews rather loudly and goes to the toilet (urinating) immediately after he managed a few licks. He also vomits up pinkish, foamy liquid at times and his stool ranges from very solid to very loose.
I am trying to entice him with his favorite food but it appears as if eating causes him discomfort.
He is still drinking water. Lately, he has started isolating himself and is a bit grumpy with the other cats.
He still likes to come for a cuddle and sleeps and cuddles with me when I go to bed.
What do you think? What should I do for one of the best friends I ever had?
I would appreciate your insight.
Warm regard
Maryke

Answer
Maryke,

I am not a vet, but the large amount of water consumption is often a warning sign that the kidneys are going! I understand that the kidneys have to be about 70% gone before the kidney numbers in blood work reflect the problem. So, if the litter pan Buddy uses is saturated quickly and Buddy is not really concentrating his urine (your vet can test this), I would say this is a clear indicator that the kidneys are not doing the job.

Given that kidney failure is the biggest killer of domestic cats, I would guess that Buddy is in kidney failure, and, there is nothing that can be done except to try to keep him comfortable. I would guess that the anemia is a result of the possible kidney problem.

The hardest thing is to know when it is time to let go.  You have to decide when Buddy's quality of life has become so poor that he is miserable. At age 16, Buddy has done very well, but is nearing the end.  I usually quote 12-15 years of age as a reasonable lifespan for indoor domestic cats.

Please let me know what you decide.

Concerned regards... Norm.