Yes usually caused by internal egg laying.According to medical articles it is chronic w/no cure. So heartbreaking.
But it can also be caused from liver and kidney damage. So either way it’s likely a chronic issue for her. She is over 5, and that’s usually when these layers start to act up.
I will keep her on aspirin like I do with Red Hen. It has been shown to help reduce inflammation so hopefully it can help her. Also help with any pain management.
Whether it’s horses, chickens or people, getting old sucks!

