My Boyfriend, 54 Yrs Old, Had A Double Bypass Surgery

My boyfriend, 54 yrs old, had a double bypass surgery and coratid artery surgery and then had another surgery that was the other coratid artery. Since coming home from surgery, he ended up in ER because his chest/ribs hurt so much for him to breath. They prescribed in Colchicine .6mg, kept him overnight and told us he had pericardial inflammation and fluid in his lungs and around his heart. He took the meds for 2 wks - suffering from diarrhea due to meds, met with heart Doctor and was taken off the meds and just started feeling better for about 3 wks...now he is having breathing trouble again, after 4 days he started using left over Colchicne and goes for echocardiogram tomorrow morning. My question is, what keeps making him fill up with fluid...at least that is what we think is happening.
If you answer this, I thank you very much in advance
Regards, Terrie and Kurt