Fluid On Lung

Hi

my husband just had about 2 liters of fluid drained from his left lung and the first x-ray before that drained the lung showed a small mass, which of course they are going to do a biopsy and send the fluid down for a culture.

He had a hard time breathing and was constantly burping, which is why he went through emergency.

Mind you, I have been asking him to go see about it for several months now.

My question is what could possibably cause this fluid in his lungs and he also drinks.

Thanks

karen