For all of you wanting updates on this type of problem: As stated by others previously, there are several problems that can cause fluid to accumulate in the abdomen (ascites). While none of the diagnoses are particularly favorable, some are more treatable than others. I have a Rhode Island Red of unknown age (but at least 3 or 4 years) that stopped laying a year ago and started accumulating fluid in the abdomen (with the accompanying waddling, lack of energy, and mouth breathing at times). I drained the fluid from her abdomen (I'm a vet, though with limited chicken experience) several times over the next few months, sometimes getting as much as 400-500ml at a time. I am happy to update that this hen is still alive a year later. She still has her good days and bad days, but she's still in the front row when it comes to mealworm frenzy time! I have had 2 other hens with the problem in the past 2 years that were not so fortunate and succumbed after having their abdomen drained 2-3 times. Regardless, I do believe it makes them feel better for whatever time they have left, so I will continue to do it when needed. I have not done necropsies on any of my hens to get definitive answers. It's hard because they all have names and are my pets on the farm.