diagnostically indicated when there is concern for a noninfectious cause of the collection Gram stain and culture should always be sent when pleural fluid is available Nucleic acid amplification testing through polymerase chain reaction (PCR) or specific antigen testing of pleural fluid may increase the likelihood of pathogen detection, particularly in patients who have been partially treated with antibiotics Fluid should be sent for a cell count with differential since this can help distinguish between various infectious pathogens and malignancy Cytology should be sent as well when malignancy is suspected Analysis of other pleural fluid parameters that have historically been assessed such as pH, LDH, glucose, and protein have been used to predict the need for further interventions, but are not routinely required as they rarely alter management Thin, free-flowing pleural fluid may sometimes be managed by simple thoracentesis (which may be repeated as needed) or the effusion may resolve as the underlying condition is treated Alternatively, a small-diameter tube, such as an 8F to 12F pigtail percutaneous tube, can be placed in the anterior or midaxillary line Early and continued administration of fibrinolytics into the catheter can be helpful in fostering resorption and preventing fibrin and other products from obstructing tube drainage Thick fluid, such as blood, pus, and sometimes chyle, often requires the placement of a larger diameter tube Either tube must be attached to a pleural drainage system When the drainage decreases significantly, to approximately mL/lb of body weight per day, the drain may be removed The drain should not be removed in the presence of an accompanying “air leak” caused by a bronchopleural connection See section below on empyema for discussion of further drainage modalities Disposition Pleural effusions that require drainage or further diagnostic evaluation clearly warrant inpatient admission There is a role for outpatient antibiotic therapy in the setting of very small effusion in the well-appearing child who has close followup Please refer to the pneumonia clinical pathway for suggested empiric antibiotic therapy (https://www.chop.edu/clinical-pathway/pneumoniacommunity-acquired-clinical-pathway ) This should be tailored, however, to local sensitivities for common pathogens Empyema Goals of Treatment The goals of treatment for empyema include the provision of adequate antibiotic treatment for the underlying infection and evacuation of significant pleural