Approach to managing parapneumonic effusion and thoracic empyema

Parapneumonic effusion is a collection of fluid in the pleural cavity, secondary to pneumonia; it occurs in up to 50% of pneumonia cases. Monitor patients with parapneumonic effusion closely because the presence of an effusion predicts poorer clinical outcomes (eg increased 30-day mortality, prolonged hospital stay)Dean, 2016. Parapneumonic effusions typically exist on a spectrum between simple and complicated effusions, rather than discrete statesAddala, 2021. If a complicated parapneumonic effusion is not managed appropriately (eg with drainage), it can progress to an empyema. The management of parapneumonic effusion is guided by the size and complexity of the effusion, and the likelihood of progression to an empyema.

Thoracic empyema can also occur in the absence of pneumonia, such as from:

haematogenous seeding
thoracic trauma or haemothorax
a long-term indwelling pleural catheter-associated infection
a surgical site infection.

Definitions and management of parapneumonic effusion and thoracic empyema summarises the definitions and management of parapneumonic effusion and thoracic empyema.

In adults, management of parapneumonic effusions and thoracic empyema may also involve nonantibiotic interventions, such as drainage, intrapleural enzyme therapy and surgery. For the management of malignant pleural effusions, see Management of malignant pleural effusion in adults.

In children, seek specialist advice for non-antibiotic management of parapneumonic effusion and empyema. Information on the diagnosis and management of parapneumonic effusion and empyema is available from The Royal Children’s Hospital (Melbourne) website.

Table 1. Definitions and management of parapneumonic effusion and thoracic empyema
simple parapneumonic effusion complicated parapneumonic effusion empyema associated with pneumonia or thoracic empyema of uncertain source thoracic empyema complicating thoracic trauma or haemothorax thoracic empyema complicating long-term indwelling pleural catheter thoracic empyema secondary to haematogenous seeding thoracic empyema associated with surgical site infection
simple parapneumonic effusion
Definition	diagnostic ultrasound available: effusion with anechoic appearance on thoracic ultrasoundAddala, 2021 Davies, 2010 diagnostic ultrasound not available: incidental small effusion (eg depth less than 10 mm on lateral decubitus X-ray)Tsujimoto, 2015
Management	Pleural fluid sampling and drainage may be required, unless an alternate noninfective aetiology is apparent (ie chronic kidney failure or hepatic hydrothorax). For indications for drainage in adults, see Drainage of parapneumonic effusion and thoracic empyema in adults; seek expert advice for children. Hospital admission is not required, unless indicated for pneumonia. No change to standard therapy for pneumonia is needed; see here for links to antibiotic regimens. Closely monitor and follow up the patient to ensure the effusion does not progress. This may be via chest X-ray or thoracic ultrasoundDean, 2016.
complicated parapneumonic effusion
Definition	diagnostic ultrasound available: effusion with echogenic appearances, loculation or septation on ultrasoundAddala, 2021 Davies, 2010 diagnostic ultrasound not available: clinically significant effusion (eg depth greater than 10 mm on lateral decubitus X-ray or greater than 30 mm on CTTsujimoto, 2015; dyspnoea attributable to effusion)
Management	Collect pleural fluid samples (see Overview of pleural effusion in adults) to analyse forAddala, 2021: biochemistry (which may include pH, lactate dehydrogenase [LDH], protein and glucose) cytology culture. Drainage is often required – for indications in adults, see Drainage of parapneumonic effusion and thoracic empyema in adults; seek expert advice for children. Admit the patient to hospital for treatment with intravenous antibiotics. The choice of regimen depends on the type of pneumonia: for community-acquired pneumonia in adults, see here for community-acquired pneumonia in children, see here for hospital-acquired pneumonia in adults and children, see here. Seek expert opinion on whether intrapleural enzyme therapy is indicated for adults.
empyema associated with pneumonia or thoracic empyema of uncertain source
Definition	a collection of pus or biochemical evidence of empyema in the pleural space effusion has echogenic appearances, loculation or septation on ultrasound (if available)Addala, 2021 Davies, 2010
Management	Collect pleural fluid samples (see Overview of pleural effusion in adults) to analyse for Addala, 2021: biochemistry (which may include pH, lactate dehydrogenase [LDH], protein and glucose) cytology culture. Empyema always requires drainage (for information on drainage in adults, see Drainage of parapneumonic effusion and thoracic empyema in adults). Admit the patient to hospital for treatment with intravenous antibiotics. The choice of regimen depends on the type of pneumonia (or presumed pneumonia, in the absence of confirmed pneumonia or chest consolidation): for community-acquired pneumonia in adults, see here for community-acquired pneumonia in children, see here for hospital-acquired pneumonia in adults and children, see here. Intrapleural enzyme therapy may be needed for adults with empyema that is not resolving despite an adequately sited intercostal catheter for drainage.
thoracic empyema complicating thoracic trauma or haemothorax
Definition	a collection of pus in the pleural space associated with active infection following thoracic trauma or haemothorax (pleural bleeding) associated with complex features of pleural ultrasound (eg echogenicity, loculation, stranding)
Management	Collect pleural fluid samples (see Overview of pleural effusion in adults) to analyse forAddala, 2021: biochemistry (which may include pH, lactate dehydrogenase [LDH], protein and glucose) cytology culture. Appropriate drainage is recommended, with either intercostal catheters or surgical decortication is recommendedMandal, 1997. Admit the patient to hospital for treatment with intravenous antibiotics. The choice of regimen depends on the mechanism of injury; treatment for skin flora including staphylococci is typically indicatedHassan, 2021. For antibiotic regimens, see here. Intrapleural enzyme therapy is usually avoided because of the risk of bleeding complications and should only be used following expert advice from a respiratory physician or cardiothoracic surgeonFoo, 2021.
thoracic empyema complicating long-term indwelling pleural catheter
Definition	a collection of pus in the pleural space associated with active infection and a long-term indwelling pleural catheter
Management	Collect pleural fluid samples (see Overview of pleural effusion in adults) to analyse forAddala, 2021: biochemistry (which may include pH, lactate dehydrogenase [LDH], protein and glucose) cytology culture. Appropriate drainage is required and may be achieved by the indwelling catheter. Interpretation of pleural fluid biochemistry is challenging. In the absence of frank pus or microbiologically confirmed infection, distinguishing infected loculated malignant effusions from those that are noninfective is difficult – seek expert advice from respiratory and infectious diseases physiciansPsallidas, 2016. For management of noninfective malignant pleural effusion, see Management of malignant pleural effusion in adults. Admit the patient to hospital for treatment with intravenous antibiotics. Antibiotic therapy with activity against skin flora including staphylococci is typically indicatedFysh, 2013. For antibiotic regimens, see here. Intrapleural enzyme therapy is typically indicated in adults, although fewer doses may be required compared with use for parapneumonic empyema – seek expert advice. Catheter removal may not be required if infection is controlled with regular drainageLui, 2016.
thoracic empyema secondary to haematogenous seeding
Definition	a collection of pus in the pleural space secondary to seeding from active bacteraemia
Management	Collect pleural fluid samples (see Overview of pleural effusion in adults) to analyse forAddala, 2021: biochemistry (which may include pH, lactate dehydrogenase [LDH], protein and glucose) cytology culture. Appropriate drainage is recommendedMandal, 1997. Admit the patient to hospital for treatment with intravenous antibiotics. The choice of regimen and duration of intravenous therapy depends on the underlying bacteraemia and either the presence of concomitant hospital-acquired pneumonia or, in people who inject drugs, right-sided infective endocarditis Hassan, 2021. Intrapleural enzyme therapy may be needed for adults with empyema that is not resolving despite an adequately sited intercostal catheter for drainage – seek expert advice.
thoracic empyema associated with surgical site infection
Definition	a collection of pus in the pleural space secondary to a surgical site infection
Management	Manage as a deep incisional surgical site infection with appropriate drainage.
Note: CT = computed tomography