So, I did an "autopsy"on my old girl after she passed and you were correct, she was full of fluidDid you pick her up? If so, did her belly feel like a big, squishy ball? I have seen a couple older hens who swelled up like that due to ascites, an accumulation of fluid in the body cavity of the bird. The two I have seen were suffering from internal laying and the resultant infection caused the ascites. They had to be culled.