My son's cat Goku (15 years old) has been having a few issues this past month, but nothing we could put our finger on and say something may be wrong. It mostly appeared to be behavioral, and yet...not understandable behavioral issues. But despite how it appeared, I did notice he was eating more and losing weight. Still, he stayed actively taunting the dog; running to his bowl if you shook the "Temptations" box - acting like he was perfectly fine, so the other symptoms just didn't seem that crucial since he didn't act sick at all.
Well, he was very sick, we just never knew it. He had suddenly stopped using the litter box about a week or so ago. Then suddenly yesterday he didn't want to eat - unheard of with this cat. By last night he had stopped drinking; by today he had stopped using the bathroom...and worse, he stopped moving. He lay down and didn't get up. I raced him to the Emergency Veterinary Hospital.
All the fancy expensive tests they wanted to order, we couldn't afford. So I opted for a low cost X-ray and Ultrasound as an exploratory action. It turns out Goku was eaten up with cancer. His liver was no longer viable, the primary liver cancer had metastasized to his lymph nodes and was now systematic. He would have died within a day on his own had I not brought him in - and suffered. So I'm glad the Veterinarian was there to at least ease that for him.
My son left work and met me at the Vets. We said goodbye to our Awesome companion for the last 15 years. We will love you forever, Goku.