Simple vs. Complex Effusion
	l Exudate, transudate, chylous l Defined by lab data l pH, glucose, protein, LDH, cell count and differential l Not always good correlation with radiographic appearance at CXR and CT l Simple: l free layering, no pleural thickening l Empyema: l often loculated, with smoothly thickened, enhancing pleura = “split pleura” sign l May have air within it, multiple loculations l CT often reveals unexpected effusion and loculation