I have experiencd that condition. I have RCC - 3b which was diagnosed in Oct, 2005. I've been on Nexavar, Sutent, Chemo, and now Torisel. Last summer, after 18 months of progression free results on Sutent, I developed "Pleural Effusions" with is fluid in the lining of the lung.
I had 2 liters drained (via Thoracentesis), then in about 3 weeks it got much worse. I had thorasic surgery and "Pleuraldesis" where they removed 4 liters of fluid, sealed the area with talc, and inserted a tube for draining more fluid. I had no more fluid for 8 months, then recently it started to return. I expect to have a thoracentesis to drain the fluid this week. Not sure what is next.
Here is more info: http://en.wikipedia.org/wiki/Pleural_effusion
Good luck to your father.
D. J.