In this x-ray, the chest cavity is at top and should be dark on both sides. This is where the lungs usually are, but in her case, one of this is being pushed out of the way.
One of our foster cats had a slight cough that sounded suspicious, turns out she has a perforated diaphragm and her spleen is intruding into her chest cavity. It’s not currently life threatening, but surgery has been prescribed and we’ll set up a time soon to get things corrected.
The fact that you are willing to do this for you cats is freaking awesome. You are a great cat-dad.
Thanks, this round of fosters has been exceptionally emotionally taxing.