Your poor cat, and poor you too :( I know exactly how you feel. My cat had kidney failure. To be blunt, the toxins build up in the blood and can lead to a kind of senile dementia as the toxins attack the brain. My cat started to pace about in an uncertain, bewildered way and used to make a pitiful howling sound in the middle of the night, She then started to forget to use the litter tray and coudn't groom herself anymore The option the vet gave was for them to take her in and attach her to an drip for a couple of days to flush the system through and she'd live on medication for her remaining life, which he predicted wouldn't be long. I knew this would be terrible for her as she was very timid and scared of her own shadow so staying at the surgery would have been traumatic for her. I had to make the hardest decision of my life but as she had no quality of life at all and was extremely distressed I asked the vet put her to sleep. It broke my heart but I couldn't face her suffering anymore. Still miss her and always will, so my thoughts are with you xx