That looks just like the stuff the doc drained off my husbands knee. It also looks like the stuff I drain out of the ball of fluid that keeps building up on the base of the tail/spine of my old cat. FYI, the fluid off my husbands knee was not infected. I don't know about my cat, since I just keep draining it when it gets golfball size. My husbands knee was because of inflammation from an injury. Cat, idk, but I'm thinking inflammation, irritation.Found standing like a penguin, very thin, lots of fluid in her belly. Drained some fluid and was able to palpate lumps in her abdominal cavity that shouldn't be there. This is what the fluid looked like:There was more in there, but I couldn't get it out. Will start on antibiotics, but will cull if I don't see a drastic improvement in 2-3 days. Note the color... seems to be blood in it. -Kathy