air sac problem on dibiliated neurological hen

I took in a feral hen (I rehab mainly wild birds) who was seen having what looked like a neurological problem. I am not so sure about that, but the bird was weak enough to be catch-able. What I do notice is that is that the hen has a very large lump (bigger than a ping-pong ball) on the right front near the crop. At first I thought it was a tumor or infection, but when I expressed it, just air came out. (Of course, the air bubble keeps coming back up). The really odd thing is, when I do express the air all the way, it sounds as if I can hear air gurgling into the crop. I have no idea what is going on, and no real history about the bird except that is was seen around for quite awhile with other feral birds, but very recently appeared to be walking, then stopping and staring off at the ground. I do know the bird is very dehydrated. I just don't think an regular air sac rupture would have left her in such bad condition. I am wondering if the "condition" has led to this bubble problem.

I have sub-Qed her, and she has perked up. However, she is not yet eating or drinking on her own, possibly because of discomfort/pressure caused by that bubble. I have started her on baytril, and also began a 4 in 1 medication (cocci, worming, etc) that is used for pigeons. Has anyone ever seen an air bubble that seems to actually go into part of the crop (air exiting in the crop)? The bird does not have any external injuries (except minor scrapes where a rooster was picking on her head when she was down).

Thanks so much.

Phyllis, Island Birder