Parapneumonic Pleural Effusions And Empyema Thoracis


Article Author:
Eman Shebl


Article Editor:
Manju Paul


Editors In Chief:
Jessica Snowden
Asif Noor
H Davies


Managing Editors:
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Frank Smeeks
Kristina Soman-Faulkner
Benjamin Eovaldi
Radia Jamil
Sobhan Daneshfar
Saad Nazir
William Gossman
Pritesh Sheth
Hassam Zulfiqar
Navid Mahabadi
Steve Bhimji
John Shell
Matthew Varacallo
Ahmad Malik
Mark Pellegrini
James Hughes
Beata Beatty
Hajira Basit
Phillip Hynes


Updated:
5/5/2019 11:40:25 PM

Introduction

A parapneumonic effusion refers to the accumulation of exudative pleural fluid associated with an ipsilateral lung infection, mainly pneumonia. Parapneumonic effusions are mainly associated with bacterial infections.[1]

Parapneumonic pleural effusions are classified into:

  • Uncomplicated parapneumonic effusions, which are exudative,  neutrophilic effusion. Gram stain and culture are negative, glucose level greater than 60 mg/dl, pH above 7.20.
  • Complicated parapneumonic effusions, resulting from a bacterial introduction into the pleura. In this type of parapneumonic effusion, there is a decreased glucose level, pleural fluid is below 7.20. Cultures of fluid from complicated parapneumonic effusions are negative and rapid bacterial clearance from the pleural space, or low bacterial count may explain this. The fluid termed as complicated because it necessitates drainage for resolution.
  • Empyema thoracis in which there is frank pus in the pleural space, or there is evidence of bacterial infection of the pleural fluid by Gram stain or a positive culture.[2][3]

Etiology

Pneumonia is the most frequent cause of parapneumonic effusions and empyema thoracis. Empyema may result as a complication of cardiothoracic surgery. Trauma can also lead to infection of the pleural space. The infecting organism may have spread from blood or other organs into the pleural space.[4][5]

Risk Factors

There are risk factors for empyema like age and comorbidities such as diabetes.[4]

Bacteriology

Streptococcus pneumoniae and Staphylococcus aureus are responsible for about 70% of aerobic gram-positive cultures. Klebsiella, Pseudomonas, and Haemophilus species are the commonest in gram-negative culture. Bacteroides and Peptostreptococcus species are the commonest anaerobic organisms. In empyema thoracis associated with aspiration pneumonia mixed bacterial florae containing aerobic and anaerobic bacteria are common. The common organism in cases of empyema thoracis complicating surgery is S. aureus.[4][6]

Epidemiology

Parapneumonic effusion develops in about 20% to 40% of patients hospitalized with pneumonia. Approximately 1 million patients develop parapneumonic effusion annually in the United States.[2][7]

Pathophysiology

 The stages of parapneumonic effusion are:

  1. Exudative stage, in which there is an accumulation of fluid in the pleural space due to increased capillary permeability that results from proinflammatory cytokines, such as interleukin 8 (IL-8) and tumor necrosis factor alpha (TNF-a). The pleural fluid in this early stage is usually clear exudative fluid with a predominance of neutrophils. Pleural fluid in this stage is simple parapneumonic effusion that usually resolves with adequate antibiotic treatment of pneumonia without the need for drainage. This stage takes approximately 2 to 5 days from the onset of pneumonia.
  2. Fibrinopurulent stage, which can develop if adequate treatment is not provided. In this stage there is a deposition of fibrin clots and fibrin membranes in the pleural cavity, leading to fluid loculations. This stage takes about 5 to 10 days after pneumonia onset.
  3. Organizing stage, in which fibrin membranes are transformed by fibroblast into a thick nonelastic pleural peel, resulting in the trapped lung with restrictive respiratory dysfunction. This stage may take about 2 to 3 weeks to develop.

The clinical course varies from spontaneous healing to chronic empyema and fibro-thorax with trapped restricted lung.[8]

History and Physical

The clinical manifestations of parapneumonic effusion or empyema are related to various factors like the presentation timing and the virulence of the causative organism. Common symptoms of bacterial pneumonia with parapneumonic effusion include a cough, expectoration, and a rise in body temperature, pleuritic chest pain, and difficulty breathing.

In most patients the following clinical signs are present in clinical examination and include:

  • Fever, tachypnea, and tachycardia
  • Pleural effusion (dullness to percussion decreased tactile fremitus and decreased or absent breath sounds)
  • Adjacent pneumonia (rales or crackles and/or bronchial breath sounds)[9]

Evaluation

Radiographic Investigations

Plain chest x-ray: Pleural effusion can easily be detected by conventional radiographic. The consistency of these pleural-based densities suggests pleural fluid loculation.[1]

Chest ultrasound: Ultrasonography helps identify free or loculated pleural effusions and helps with thoracentesis guidance.[10]

Chest computed tomography (CT): For empyema or loculated effusion in adults, a CT scan with intravenous contrast is helpful. Radiographic contrast enhances visualization of the pleural surfaces and helps identify pleural fluid loculations. Empyema is suggested by the presence of split pleura sign in which there is a thickening of the visceral and parietal pleura with significant separation of the pleural surfaces. CT helps in detecting underlying parenchymal abnormalities.[11]

Thoracentesis

Diagnostic thoracentesis is needed for the management guidance of parapneumonic pleural effusion. In general, a parapneumonic effusion should be sampled if It is a free-flowing and layers greater than 10-mm on a lateral decubitus film. Radiological guidance of thoracentesis by ultrasound or chest computed tomography (CT) in some cases is helpful especially when the effusion is loculated.[12] The aspirated pleural fluid is subjected to:

  • Microbiologic analysis: Gram stain with cultures and sensitivity (aerobic and anaerobic)
  • Pleural fluid total and differential cell count
  • Biochemical analysis: Total protein, lactate dehydrogenase, glucose) and  pH
  • Pleural fluid biomarkers: Novel biomarkers of infection (e.g., C-reactive protein, procalcitonin, STREM-1) have been evaluated to help distinguish complicated parapneumonic pleural effusions from uncomplicated parapneumonic pleural effusions, but there is no proven superiority to traditional pleural biochemistries.[13][14]

More appropriate investigations should be performed to exclude other causes of pleural effusion when indicated.

Treatment / Management

Treatment of parapneumonic effusion includes appropriate antibiotic therapy together with drainage of pleural fluid as indicated. 

Parapneumonic effusion is classified into 4 groups based on risk for the poor outcome:

  • Category 1 (very low risk): The effusion is small (less than 10-mm thickness on decubitus) and free-flowing. No thoracentesis is indicated.
  • Category 2 (low risk): The effusion is small to moderate (equal to 10 mm and less than half the hemithorax) and free-flowing with negative culture and Gram stain regardless of the prior use of antibiotics and pH equal to 7.20.
  • Category 3 (moderate risk), in which one of the following criteria is present:  the fluid equal to half the hemithorax, loculated effusion, thicken pleura on contrast-enhanced CT scan, positive Gram stain or culture or pH less than 7.20.
  • Category 4 (high risk): This is when pleural fluid is in the form of pure pus.

Patients with category 1 and category 2 may not require drainage. In patients with category 3 and 4, drainage is recommended. Fibrinolytics, VATS, and surgery may be indicated for managing patients with category 3 and category 4 parapneumonic effusion not responding to less invasive drainage methods.[12]

Antibiotic Therapy

It must cover the suggested causative organisms of pneumonia according to the clinical setting. The duration of antibiotic therapy depends on many factors, for example, the sensitivity of the organism, extent of pulmonary parenchymal and pleural disease, response to initial therapy and adequacy of drainage.[15]

Chest Tube Drainage

Chest tube drainage is generally preferred for patients with uninoculated effusions and free-flowing fluid. Chest tubes are ideally inserted under ultrasound or CT-guidance. The choice of a thoracostomy tube size is controversial. Imaging performed within 24 hours is essential for documenting the correct position of the chest tube. Chest tubes are left in place until the drainage rate is less than 50 ml per day and the empyema cavity has closed.[15]

Fibrinolytic Agents 

The intrapleural administration for fibrinolytic agents (for example, streptokinase and tissue plasminogen activator) or fibrinolytic plus mucolytic agents aiming for facilitating the drainage of loculated parapneumonic effusion is controversial.[16][17]

Thoracoscopy

Thoracoscopy is an alternative therapy for loculated empyemas when antibiotics and tube thoracostomy fail for the drainage. Thoracoscopy disrupts the intrapleural adhesions and allows the drainage of the pleural fluid.[18] Previous studies showed that delay for referral for thoracoscopy more than two weeks was associated with failure of thoracoscopy and conversion to thoracotomy.[19]

Decortication 

Decortication is indicated when persistent (present after 6 months) pleural peel is formed, leading to significant pulmonary restriction.[20]

Rib Resection and Open Drainage of Pleural Space

A vertical incision through the chest wall with rib resection (1 to 3) is done to allow pleural fluid drainage. A chest tube is left in place (about 60 to 90 days). Open drainage of the pleural space may be considered when the previous methods fail, and when the patient is too ill to tolerate decortications.[20]

Prognosis

Most of the patients with parapneumonic pleural effusion recover, but the mortality rate still around 10%. Proper antibiotic therapy and pleural fluid drainage are vital for recovery.[1] Scoring systems have been studied (RAPID score) to determine which patients with parapneumonic effusions are at highest risk for a poor outcome.[21]

Complications

Complications of pleural empyema may include residual pleural thickening, extensive pleural fibrosis, bronchopleural fistula formation, and development of empyema necessitans.[22]

Pearls and Other Issues

Early diagnosis, appropriate antimicrobial therapy, and adequate drainage of parapneumonic effusion are essential for decreasing its morbidity and mortality.

Enhancing Healthcare Team Outcomes

The parapneumonic pleural effusion management requires interprofessional cooperation between physicians of the concerned specialties (e.g., pulmonary medicine, radiology, and microbiology and cardiothoracic surgery) for a good outcome. The interprofessional care provided to the patient must follow an evidence-based approach. (Level III)


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Parapneumonic Pleural Effusions And Empyema Thoracis - Questions

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A frail woman presents to you with a 2-day history of fever and a persistent cough. A chest x-ray reveals a large left pleural collection. Thoracentesis reveals a fluid with the following characteristics (pH 6.4, glucose<40, LDH>700). What is the next step for this patient?



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A 62-year-old male presents with fevers, cough, and shortness of breath. Chest radiograph shows right lower lobe pneumonia and a large pleural effusion. Lateral decubitus film shows the effusion to be 1.5 cm thick. Thoracentesis is performed. Which of the following findings would indicate a need for a tube thoracostomy?



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A 65 year old male is admitted with a 5 day history of a cough productive of rust colored sputum and fevers. He has a 40 pack year history and a history of hypertension on lisinopril. Cardiac exam is normal but the right chest is dull to percussion half way up with decreased breath sounds. Chest radiograph shows consolidation of the right lower lobe and an effusion. Select the factor that would not indicate need for a chest tube.



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An 18-month-old child is brought in with a 3-day history of cough and fever. He has been taking fluids but is not hungry. The only medication his parents have given him is acetaminophen. He has no significant past medical or travel history. Exam shows a temperature of 38.5 degrees Celsius, clear mucosa, dullness to percussion over the left lung with rhonchi, but no rashes or cardiac findings. Chest x-ray shows a left lower lobe infiltrate and opacification of the left lower half of the lung. Which of the following investigations is not needed?



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An 18-month-old is brought in with a 3-day history of cough and fever. He is diagnosed with pneumonia with parapneumonic effusion by chest X-ray. Oxygen saturation is 87 percent. What is the first therapeutic intervention?



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A 17-year-old male who lives in a homeless shelter is brought to the emergency department by emergency medical services for significant respiratory distress. He has a history of alcohol use disorder and intravenous drug use. He is admitted to the intensive care unit and intubated for respiratory failure. A chest x-ray shows a left-sided, moderate size pleural effusion with mediastinal shift and perihilar lymphadenopathy. What is the most probable cause of his pleural effusion?



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An 88-year-old female is brought to the emergency department by paramedics after her daughter found her unconscious on her kitchen floor. The patient lives with alone and has no significant medical or surgical history, but she did have viral rhinitis about two weeks ago that became increasingly severe a few days ago. The patient is somnolent and difficult to arouse, responds to her first name, but is disoriented to place and time. Temperature is 38.9 C, pulse is 92/minute, blood pressure is 138/96 mmHg, and respirations are 24 per minute. A chest x-ray reveals bilateral pleural effusion and bilateral lower lobe consolidations. Diagnostic thoracentesis was performed. Pleural fluid analysis reveals cloudy fluid with no frank pus, specific gravity of 1.433, protein 4.2 g/dL, fluid protein/serum protein 0.96, serum-ascites albumin gradient (SAAG) 0.65 g/dL, fluid LDH 0.4, and cholesterol 88 mg/dL. The patient is up to date with all vaccines including influenza and pneumococcal vaccines. What is the most appropriate next step in treating this patient?



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Parapneumonic Pleural Effusions And Empyema Thoracis - References

References

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