My mother, 86, has had a pacemaker and atrial abulation and is currently being treated for multiple myelom to which her blood work is showing great results! Her problem is that she has had fluid build up in her left lung which was drained 3 months ago, last week and the left lung has refilled again. Doctor says heart problem would cause fluid build up in both lungs, not one. Fluid tested negative for infection, myeloma cells, etc. CAT scan shows no mass in left lung. So, doctor is baffled. Any idea what can cause fluid build up repeatedly in one lung only?