Juvenile Renal Disease???

We just had to put our Great Pyr / Golden mix to sleep on Tuesday, she was 17 months old.  By the time we noticed any syptoms (symptoms) we were apparently to late, they sedated her and gave her x-rays and took a blood test on Monday, we also had her to the same vet on Sat. but she gave us rimadyl and an anti-nausea medicines.
The results from the blood tests came back on tuesday with a CREA level of 7.7 on one test and 10.9 on another, so they put her on IV fluids.  On Tuesday afternoon we drover her to a vet that had a ultrasound machine and he said 3/4 of one kidney is gone and 1/2 of the other.  Her tongue started to turn purple/black and she was breathing sporatically, so he suggested we put her to sleep and we did reluctantly since we have a littermate of hers with us also.
Could we have brought her home and made her comfortable until the end?
Can you explain why her tongue turned black?  Is this a common sign at the end?
I just don't want any regrets.......I don't want to think we could have extended her life somehow, because this all came on so fast, she seemed perfectly fine 2 weeks ago and now she is gone.
Can you please help me make sense of this.
The vet did say that it looked like something she was born with.
Thank you for any help you can give us.

[Aleda M Cheng, D.V.M., C.V.A]

I am very sorry for your sad loss.

When a pet or human is in end stage kidney failure the only options are kidney transplant or death.  

The tongue is a very important diagnostic tool.  In traditional Chinese medicine the tongue and pulses are pretty much the only diagnostic tools.  A tongue that is black means impending death so I believe that if you had not put her to sleep she would have died shortly anyway.  I think that you did the right thing, and I don't believe you could have extended her life for any length of time.  

[skyedog]

Thank you.  You made us feel a little better about our decision, I just can't shake the feeling  we should have brought her home to die and  be with her littermate and brother.
Is there a name for this black tongue?  What is the reason that her tongue turned black.  When the vet saw this he knew there wasn't much hope.  When he first saw her he thought he could do something until he opened her mouth.
thank you again.