Pleural Effusion-Parapneumonic


Parapneumonic Effusion

Parapneumonic Pleural Effusion is Defined as Pleural Effusion Which Occurs in Association with Bacterial Pneumonia, Lung Abscess, or Bronchiectasis

  • General Comments
    • However, in Some Cases, an Infected Pleural Effusion May Rarely Develop without an Apparent Adjacent Pneumonia
  • Uncomplicated Parapneumonic Effusion
    • Uncomplicated Parapneumonic Effusion is Defined as a Free-Flowing Sterile Pleural Effusion
    • Occurs with Movement of Lung Interstitial Fluid and Neutrophils Across the Visceral Pleura into the Pleural Space
    • Exudate with pH >7.2
  • Complicated Parapneumonic Effusion
    • Complicated Parapneumonic is Defined as the Bacterial Invasion of the Pleural Space, Neutrophil Influx, and Pleural Space Acidosis (Due to Anaerobic Utilization of Glucose by Neutrophils and Bacteria)
    • Exudate with pH <7.2
    • There is a Higher Incidence of Complicated Parapneumonic Effusion in Human Immunodeficiency Virus (HIV)/Acquired Immune Deficiency Syndrome (AIDS) (see Human Immunodeficiency Virus)


Various Definitions

  • Vianna Definition of Empyema (JAMA, 1971) [MEDLINE]
    • Positive Pleural Fluid Culture or Pleural White Blood Cell Count >15,000/mm3 and Pleural Total Protein >3.0 g/dL
  • Weese Definition of Empyema (Arch Intern Med, 1973) [MEDLINE]
    • Pleural White Blood Cell COunt >500/mm3, Pleural Total Protein >2.5 g/dL, or Pleural Specific Gravity >1.018
  • Modern Definition of Empyema
    • Presence of Pus in the Pleural Space and/or Positive Gram Stain of Pleural Fluid
    • Positive Pleural Fluid Cultures are Not Required for the Diagnosis of Empyema, Since Pleural Fluid Cultures May Be Negative for Multiple Reasons
      • Anaerobic Organisms are Difficult to Culture
      • Insensitivity of Bacterial Culture Methods
      • Pleural Fluid Sampling Often Occurs After a Patient Has Already Received Antibiotics
      • Pleural Fluid Sampling Errors May Occur Due to Loculations with Aspiration of a Sterile Fluid Pocket, Adjacent to an Infected Fluid Pocket


Parapneumonic Effusion

Risk Factors for Parapneumonic Effusion

Protective Effect of Inhaled Corticosteroids Against the Development of Parapneumonic Pleural Effusion (see Corticosteroids)


Risk Factors for Empyema



General Comments




Complete Blood Count (CBC) (see Complete Blood Count)

Serum Procalcitonin (see Serum Procalcitonin)

Pleural Fluid (see Thoracentesis)

Indications for Thoracentesis in the Setting of Parapneumonic Effusion (Chest, 2000) [MEDLINE]





Pleural Fluid Cell Count and Differential

Pleural Fluid pH

Pleural Fluid Glucose

Pleural Fluid Total Protein

Pleural Fluid Lactate Dehydrogenase (LDH)

Serum-Pleural Albumin Gradient (SPAG)

Pleural Fluid Cholesterol


Pleural Fluid Culture

Molecular Analysis of Pleural Fluid

Chest X-Ray (see Chest X-Ray)


Recommendations (American Association for Thoracic Surgery Emypema Guidelines 2017) (J Thorac Cardiovasc Surg, 2017)[MEDLINE]

Chest Computed Tomography CT with Intravenous Contrast (see Chest Computed Tomography)





Chest Computed Tomography (Chest CT) Findings Which Allow Differentiation of Empyema from Lung Abscess (see Lung Abscess)

Recommendations (American Association for Thoracic Surgery Emypema Guidelines 2017) (J Thorac Cardiovasc Surg, 2017)[MEDLINE]

Thoracic Ultrasound (see Thoracic Ultrasound)


Other Pleural Fluid Assays

ACCP Consensus Guidelines Classification of Parapneumonic Effusion (Chest, 2000) [MEDLINE]

Clinical Manifestations

General Comments

Time Course of Presentation

  • Time Course of Parapneumonic Effusion Depends on the Underlying Organism, Host Immunocompetence, and Timing of the Patient’s Presentation for Medical Care
    • Anerobic Emypema: may present after a longer time course (may be as long as weeks in duration)
    • Average Duration of Symptoms in Patients with Empyema Prior to Presentation is Approximately 2 wks (NEJM, 2005) [MEDLINE]

Renal/Age/Purulence/Infection Source/Dietary Factors (RAPID) Score

  • Rapid Score is Used to Risk Stratify Patients with Pleural Space Infection at Presentation
  • Study of RAPID Score in Patients (from the UK MIST1 Trial) with Pleural Space Infection at Presentation with Pneumonia (Chest, 2014) [MEDLINE]
    • Increased Age, Hospital-Acquired Infection, Non-Purulence Predicted Poor Outcome
    • Increased RAPID Score Predicted Mortality and Increased Hospital Length of Stay
  • Study of RAPID Score to Predict Long-Term Outcome in Pleural Space Infection at Presentation for Pneumonia (Ann Am Thorac Soc, 2015)
    • Increased RAPID Score Predicted Mortality Rate at 3 mo and 1/3/5 yrs
    • Factors Associated with High-Risk RAPID Scores: Gram-negative rod infections, heart disease, diabetes mellitus, lung disease, and increased length of stay
  • German Study of the Adjustment of the RAPID Score with 2 Additional Variables (Sci Rep, 2023) [MEDLINE]
    • Diabetes type 1 and 2, renal replacement therapy, immunosuppression, postoperative bleeding, intraoperative transfusion as well as microbiologically confirmed bacterial invasion of the pleura all led to higher mortality rates
    • Modifying the RAPID Score by Adding the Comorbidities Diabetes Mellitus and Need for Renal Replacement Therapy Significantly Increased the Predictive Value of the RAPID Score

Pulmonary Manifestations

Symptoms Related to Underlying Pneumonia (see Community-Acquired Pneumonia)

  • Cough with Sputum Production (see Cough)
  • Dyspnea (see Dyspnea)
  • Fever (see Fever)
  • Pleuritic Chest Pain (see Chest Pain)
  • Physical Exam Findings
    • Crackles
    • Egophony (E to A Changes)
    • Increased Tactile Fremitus
  • Sepsis (see Sepsis)

Symptoms Related to Parapneumonic Pleural Effusion/Empyema

  • Dyspnea (see Dyspnea)
  • Empyema Necessitatis: spontaneous drainage of empyema via fistula through the chest wall
  • Fever (see Fever)
  • Pleuritic Chest Pain (see Chest Pain)
  • Weight Loss (seeWeight Loss)
  • Physical Exam Findings
    • Decreased Breath Sounds
    • Decreased Tactile Fremitus
    • Dullness to Percussion
  • Sepsis (see Sepsis)

Symptoms in Cases of Post-Pneumonectomy Empyema

  • Fever (see Fever)
  • Shift of Mediastinum to Contralateral Side: normally, mediastinum shifts to ipsilateral side as it fills with fluid over days-weeks post-procedure
  • Expectoration of Large Amounts of Pleural Fluid
  • Presence of Air-Fluid Level within the Pneumonectomized Space
  • Drainage of Purulent Material from Surgical Incisions


Treatment Recommendations by Class

Treatment Recommendations by Category (ACCP Consensus Guidelines) (Chest, 2000) [MEDLINE]


Chest Tube (Tube Thoracostomy) (see Chest Tube)

Intrapleural Deoxyribonuclease (DNase) (see Dornase Alfa)

General Comments


Clinical Efficacy

Intrapleural Thrombolytics (see Thrombolytics)


Clinical Efficacy

Video-Assisted Thoracoscopic Surgery (VATS) (see Video-Assisted Thoracoscopic Surgery)