What duration of antibiotic therapy do you use for a loculated parapneumonic effusion that does not meet criteria for empyema?  

Could you please clarify which criteria are missing to call it empyema? Was the pH above 7.20 or is it not an exudate by Light's criteria?  The most appropriate medical treatment for a loculated effusion from infection (assuming it is not malignant) would be tPa/DNase with systemic antibiotic...

Empyema simply means pus in a body cavity. There are no diagnostic laboratory criteria. It is a diagnosis made based on the visual and physical characteristics of the fluid, and not laboratory findings. There are some terms that are misnomers and inappropriately use the term "empyema" (such as "spon...

A total of six weeks of antibiotic therapy, including empirical anaerobic coverage if the microbiology of the pleural space infection is not definitively established, for complicated parapneumonic effusion or empyema. The antibiotic approach is akin to that for a lung abscess.