Aww.
I cried when our cat died in August 2011. Had the lil' guy for about 11 years and he wasn't a baby when we got him.
His urinary track got backed up and his kidneys also failed, among other complications as a result; something to do with his blood went bad, I forget what exactly. Shockingly bad levels of toxins or something?
Went through surgery to release the urine, but was too far gone. We had the option to do a second lot of surgery but we were told that afterwards he would almost certainly end up in intensive care where he would be kept alive until later dying. We were given that option if we wanted time to say goodbye. Chose to avoid the trauma of that for the better of the cat and the family.
It really sucks when you lose a childhood pet. When you have a cat that bums around for a year or two and annoys you, maybe not so much. Either way it sucks.
One of my cats, EashaVe, died on August 1st, 2010. She died of a rare and exhausting cancer. I spent over 5 grand ensuring she could live a prolonged, and quality-filled life. I didn't want her to suffer, but I wanted her to live out her life as long as possible (she was about 9 when this happened). Eventually, the flueds hit her lungs and she couldn't breath well, so we called out someone to uethanize her.
After that, we took in a cat with a huge neck injury, permanently roostering her head. My brother's friend was moving, and the cat that belonged to his now deceased mother they didn't want (can't figure out why, he's adorable and sweet). Then, we rescued 3 cats from a shelter, all ones that people didn't want/were a bit more hostile.
We then took in a neighbor's cat who, after 15 years (both of their kids are younger than the cat, have lived with her their entire life), they simply wanted to get rid of. She was old, so we knew we'd be getting into some issues, and our neighbor's response was "put her down if she has any issues," which was pathetic on almost every level of compassion. Due to the stress of 6 other cats, when she hadn't ever lived with 1, and high blood pressure, her retnas detatched, and she lost her sight. However, because of how quick we caught it, they reattached. Sadly, after this, she simply couldn't push any further. She would've had to live on an IMMENSE amount of flueds for the rest of her life, which simply doesn't work.
My oldest cat may have lymphoma, but nothing's been officially diagnosed.
You have my condolences, Shortcut. I've been through similar situations and I know how rough it can be.