What does "opacity in the left lower zone with obliteration of the left costophrenic angle-pleural effusion" mean?

Density on xray: On the views of the chest x-ray or ct there is density at the base of the left lung cavity junction with the diaphragm costo-phrenic angle is that area. Could be fluid=effusion, or blood or scar. The density varies with the nature of the fluid.

CT: Means axactly that. Should obtain a cat scan thorax to really asses that area and decide if further intervention advised.