Swelled Butt?

[Ringtailtwister]

Can any one tell me what is wrong with my hen's butt? It is swollen and soft to the touch like its full of fluid. It doesn't seem to bother her she eats and does her normal hen things ok. Here is a picture of the swollen place.

 

[Yorkshire Coop]

Could be ascites (Build up of fluid in the abdomen)
Check out this thread ~ https://www.backyardchickens.com/t/617171/chicken-with-swollen-abdomen-how-do-i-help-her
Check out the links too in Speckled hens post in that thread.

Good luck with her