Investigation

The investigation of a patients with suspected empyema should include the following: (1)

• imaging
  • chest X-ray - pleural effusions are usually identified as a result of clinical examination and chest radiography
    • further assessment
      • ultrasound scanning is more sensitive and specific than a plain X-ray, allows estimation of volume, localisation of effusions and assessment of loculation, and is often the initial investigation used to guide aspiration
      • contrast-enhanced CT scanning may provide additional discrimination (e.g. distinguishing empyema from parenchymal lung abscess) (2) but should be reserved for complicated cases or if there is doubt about the diagnosis
• full blood count:
  • reveals a polymorphonuclear leucocytosis
    
    
• pleural fluid aspiration:
  • may be diagnostic
  • the features of a the aspirate from a classical empyema are:
    • leucocytosis
    • organisms on culture or gram staining
    • reduced glucose
    • low pH

Reference:

1. Shen KR, Bribriesco A, Crabtree T, et al. The American Association for Thoracic Surgery consensus guidelines for the management of empyema. J Thorac Cardiovasc Surg. 2017 Jun;153(6):e129-46.
2. Kearney SE, Davies CW, Davies RJ, et al. Computed tomography and ultrasound in parapneumonic effusions and empyema. Clin Radiol. 2000 Jul;55(7):542-7.