A few months ago our dog broke his chain and attacked one of our pet hens who was sitting on eggs at the time. Feather was a hand raised family pet, who frequently went broody and more often then not liked to sit on her hoard of secretly laid eggs. He chased her, and it was fortunate at all, that we managed to rescue her from his jaws, before he did any further damage.
She had suffered lacerations to the neck and head area, but with good care she soon seemed to recover. But what we didn't know was that she had been damaged internally. She seemed to be doing quite well and resumed egg laying, however the eggs seemed to be an unusual shape and now and them we could hear her cackling whenever she laid.
On afternoon after helping my Mum I came back down to find poor Feather sitting in a miserable heap with her intestines protruding from her cloaca. There wasn't much we could do for her, and with the kids around it made it even harder to put her out of her misery. We made her as comfortable as possible, and later that evening I went out to quietly put her down. It was fortunate for me the little hen had passed away which saved me the horrible task of having to destroy her.
A search on the internet about prolapse didn't give me many clues, I fortunately had been given an old NRM Feeds book about chickens and it described in details the different causes of prolapse in hens. In some cases the hen can be saved, the standard descriptions give advice about how to treat the condition but do not necessarily outline all of the possible causes. In Feather's situation it was due to the stress of being frightened and then attacked by our dog. I would think that his attack has also caused serious internal damage to her ovaries. We very sad to lose our little chicken.
To be honest with prolapse the kindest thing to do is to euthanise the bird rather than persist. It's better to save the chicken the suffering than to put her through any trauma. I'm a very realistic person when it comes to animals, even pets at times can end up with incurable conditions.