Poor babies! I'm sorry for the last two posters who had / have to make a tough decision.
I'm on this thread because my hen had something similar but not nearly as severe and it seemed to clear on its own. There must be a few different things going on with these girls.
Okay - I've been reading most of this thread - my girl has just started the swollen butt but has had a wheeze (audible honk when breathing in) for quite a few weeks. I came across this:
Cystic Right Oviduct
"Fluid accumulation in the vestigial right oviduct is a common finding in hens. The...