My 7 yr old beagle has been sick for about 2 months now, bad cough, had many many tests done, my vet thought it was his heart, at her suggestion, I took him to the Univ. of Penn for cardiac eval. they said he has pneumonia, after a month of antibiotics, he is still coughing, my vet did another xray of lungs wich are clear but said there is fluid in his chest cavity, has anyone heard of this and what could cause it?