Em=empyema with thickened and enhanced

pleura.

Ef=no pleural thickening and enhancement

denoting effusion and not empyema.

presence of gas inside empyema suggest

broncho-pleural fistula.
open arrow=edema and inflammation of the

extra pleural tissue.

cephalad veiw showed empyema more rounded

simulating lung abscess.

Reference:BiblioMed Textbook-Computed Body Tomography