Fluid in chest cavity.

Our precious 5 year old girl Maya had 40ml of off fluid removed from her chest cavity 4 weeks ago. Of course our vet was reluctant to definitely say it is FIP but we know that is a real possibility. She has had a string of issues since then, bout of constipation and now a UTI for witch she is taking Clavamox.  X rays taken as recently as two days ago show no fluid in the chest cavity or abdomen. Has anyone seen or heard of fluid being removed from the chest and not turning out to be FIP.

Did the vet analyze the fluid?  Did they say it was pus or chyle?  There are a lot of different things that can cause a Pleural Effusion (fluid in the chest) other than FIP, although FIP is a common cause of it.  This site talks about some of the causes of it. http://www.petmd.com/cat/conditions/respiratory/c_ct_pleural_effusion#.UrI2QrTAERA

Thank you for responding. I am not familiar with those terms but the fluid was a clear light brown color. They did test it for bacterial infection witch was negative. Another test did reveal presence of Coronavirus but they still wont make a definite decision on FIP based on that. At the time of removal of the fluid, they put her on Clavamox, witch she took for two weeks. After the third day she showed distinct signs of improvement, playing and running through the house. A few days after the antibiotics were finished she came down with what we thought was constipation. Possibly due to the fact we were giving he all the treats she wanted to eat. Vet gave her enema and  Cortisone shot for possible bowel inflammation that appeared on X ray. They also gave her IV fluids that day. Again she appeared to improve before coming down with a UTI a week later. She is now 5 days into treatment for that. Her litter box habits have returned to normal, but she in my opinion is just OK, not eating much as usual and activity level is down. Also, she has lost 2 pounds over the course of this ordeal. Thanks again.