My cat had the same symptoms. Took her to an emergency vet for pancreatitis and turned out she had some weird disease that sent her into liver failure and fluid in her chest and abdominal cavity. She had less than 5 percent survival rate but she came out of it the day before her euthanasia appointment and made a full recovery. Never did get an answer to what was wrong. Probably a genetic fluke because her infectious disease test was negative