If his kidneys are failing... there is nothing to do.
Cats given distemper vaccine sometimes develop autoimmune
kidney disease due to the cat kidney that was in the vaccine.

Once the kidneys start to fail, there are dry heaves, terrible nausea, weakness, and suffering. It can come very suddenly.
These crystals could have damaged his kidneys as well.

I know it is a terrible decision... guilt looms either way. But I know for ME... I felt terribly guilty when Sheba crashed...I thought I should have done it sooner. But she seemed to love the vacation we squeezed out of it. When I look at her portrait on vacation I don't see suffering. But one month home, and she really changed.

This is her that last summer-- 2010 I don't know if you can see it or not.
One of the vets who helped us that final day, said with her Creatinine level she should have been put to sleep in JUNE!
Dr. Brooks said we could take her on vacation! GUILT... no matter what you do, there is terrible guilt and tears. I am having tears just typing it out all over again!

One does what one has to do. You know better than any of us, in the final analysis, and you have to live with your decision either way.

We are anticipating Oreo leaving soon. I watch her like a hawk all day long. But she seems to enjoy herself and still goes outside --like today it is sunny, for 20minute or so periods. She eats, and seems comfortable still, now past her projected life
with this intestinal mass. It will be a painful day, tho in the near future sometime for us, as well.