I now have a hen, about 2-3 years old (I forget when she hatched) who has a similar problem. She's part of a large flock so I have no idea how she's been eating/pooping/laying. But recently she's been lethargic and that's when I noticed a bulge between her legs & vent. It's firm but not rock-hard, and she's got some wet poo on her butt-fluff. Sometimes she sits on the ground & seems to be gasping for breath, but she's still getting around. Last night she got back in her 2nd story coop & even got up on the roost.
I'm wondering if it would be worth a try to drain her.
Or should I leave her until she seems really unwell.
Or just cull her now.
I had another hen with a similar condition, I let her go on for several weeks until she seemed to be really suffering, then I culled her. I will be brave & cull this one sooner, if I think that's best for her.
If I don't have a hypodermic needle, what else could I use to drain her? Where should I stick her? Please advise, thank you!