Here is a short article about cystic right oviduct in hens:
https://www.merckvetmanual.com/poultry/disorders-of-the-reproductive-system/cystic-right-oviduct-in-poultry
And another with pictures...
When you drain the belly and get clear colorless fluid, that is from a chicken having a cystic right oviduct, not ascites (water belly.) Female chickens are born with a right and left oviduct, but the right oviduct normally shrivels and is not functional. If a chicken is exposed to a respiratory...