Pleural empyema

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A ~~pleural~~Pleural-thoracic empyema (or commonly referred simply as an empyema) refers to an infected purulent and often loculated pleural effusion, and is a cause of a large unilateral pleural collection. It is a potentially life-threatening condition requiring prompt diagnosis and treatment.

Epidemiology

Empyemas are usually the complication of another underlying abnormality, and thus demographics will follow those of the primary cause, e.g. pneumonia, sub-diaphragmatic abscess, oesophageal perforation etc...

Patients with HIV ~~/ AIDS~~/AIDS are more likely to have pneumonia, and in turn are more likely to develop an empyema, which may occur in over 5% of cases of pneumonia ⁵.

Clinical presentation

Clinical signs and symptoms in isolation are non-specific, and mimic pulmonary infection of any compartment, with fever and increased white cell count being common. In the setting of a pleural collection, consolidation and infective symptoms, imaging alone is unable to exclude infection, and thoracocentesis with microbiological assessment is required. Presence of gas locules within the collection or thickened enhancing pleural margins are strongly indicative of infection (see below).

Additionally the presumptive diagnosis can be made if the fluid pH is &lt~~; 7~~;7.0 or the fluid has glucose level &lt~~; 40mg~~;40mg/dL ⁴.

Pathology

Microbiology

Offending organisms vary somewhat according to the age at which the empyema develops and the underlying abnormality ~~/ primary~~/primary site of infection. For parapneumonic empyemas most frequent organisms are ^9-107,9:

childhood
- Pneumococcus
adults
- penicillin-resistant staphylococcus
- gram-negative bacteria
- anaerobic bacteria: usually polymicrobial

In the setting of trauma or thoracic surgery staphylococcus aureus is usually involved ¹⁰⁷.

Radiographic features

Plain film

Can resemble a pleural effusion and can mimic a peripheral pulmonary abscess, although a number of features usually enable distinction between the two (see empyema vs lung abscess) ³. Pleural fluid is typically unilateral or markedly asymmetric ⁴. Generally empyemas form an obtuse angle with the chest wall, and due to their lenticular shape are much larger in one projection (e.g. frontal) compared to the orthogonal projection (e.g. lateral) ³. The lenticular shape (bi-convex) is also suggestive of the diagnosis, as transudative ~~/ sterile~~/sterile pleural effusions tend to be cresentic in shape (i.e concave towards the lung, see empyema vs pleural effusion).

Ultrasound

The appearances of an empyema depend on the composition of the collection. Typically they are not uniformly anechoic and are often often septated.

Ultrasound has a major role in enabling targeted thoracocentesis.

CT

Typically appears as a fluid density collection in the pleural space, sometimes with locules of gas. They form obtuse angles with the adjacent lung, which is displaced and compressed. The pleura is thickened due to fibrin deposition and in-growth of vessels with enhancement. At the margins of the empyema, the pleura can be seen dividing into parietal and visceral layers, the so-called split pleura sign, which is the most sensitive and specific sign on CT, and is helpful in distinguishing an empyema from a peripheral lung abscess (see empyema vs lung abscess) ^2-3. The inner walls of the empyema are smooth.

Treatment and prognosis

Prompt evacuation of the infected fluid along with appropriate antibiotics is the mainstay of treatment, and will not only improve survival but also hopefully prevent the formation of a fibrothorax.

Evacuation may be performed with percutaneous chest tube placement often with administration of fibrinolytic agent (e.g. streptokinase or urokinase ⁸) into the pleural space to break down septations. Alternatively video-assisted thoracic surgery (VATS), open decortication, or even Clagett thoracotomy may be performed. VATS is increasingly thought to lead to faster resolution with lower morbidity and reduced cost ^5-6.

Prognosis is not surprisingly worse in HIV ~~/ AIDS~~/AIDS patients with reduced CD₄ counts ⁵.

Trivia

Baron Guillaume Dupuytren (of Dupuytren contracture fame) Bonaparte died of an empyema in 1835 ^6,7.

Differential diagnosis

General imaging differential considerations include

pleural effusion from other causes, especially in the setting of inflammatory conditions
- systemic lupus erythematosus (SLE)
- rheumatoid arthritis
- Dressler syndrome (post myocardial infarction)
hiatus hernia (AP film)
lung abscess: seeempyema vs lung abscess
cavitating lung lesion

-<p>A <strong>pleural-thoracic empyema</strong> (or commonly referred simply as an <strong>empyema</strong>) refers to an infected purulent and often loculated <a href="/articles/pleural-effusion">pleural effusion</a>, and is a cause of a <a href="/articles/large-unilateral-pleural-effusion">large unilateral pleural collection</a>. It is a potentially life-threatening condition requiring prompt diagnosis and treatment.</p><h4>Epidemiology</h4><p>Empyemas are usually the complication of another underlying abnormality, and thus demographics will follow those of the primary cause e.g. pneumonia, sub-diaphragmatic abscess, oesophageal perforation etc..</p><p>Patients with HIV / AIDS are more likely to have pneumonia, and in turn are more likely to develop an empyema, which may occur in over 5% of cases of pneumonia <sup>5</sup>.</p><h4>Clinical presentation</h4><p>Clinical signs and symptoms in isolation are non-specific, and mimic pulmonary infection of any compartment, with fever and increased white cell count being common. In the setting of a pleural collection, consolidation and infective symptoms, imaging alone is unable to exclude infection, and thoracocentesis with microbiological assessment is required. Presence of gas locules within the collection or thickened enhancing pleural margins are strongly indicative of infection (see below).</p><p>Additionally the presumptive diagnosis can be made if the fluid pH is < 7.0 or the fluid has glucose level < 40mg/dL <sup>4</sup>. </p><h4>Pathology</h4><h5>Microbiology</h5><p>Offending organisms vary somewhat according to the age at which the empyema develops and the underlying abnormality / primary site of infection. For parapneumonic empyemas most frequent organisms are <sup>9-10</sup>:</p><ul>
+<p><strong>Pleural-thoracic empyema</strong> (or commonly referred simply as an <strong>empyema</strong>) refers to an infected purulent and often loculated <a href="/articles/pleural-effusion">pleural effusion</a>, and is a cause of a <a href="/articles/large-unilateral-pleural-effusion">large unilateral pleural collection</a>. It is a potentially life-threatening condition requiring prompt diagnosis and treatment.</p><h4>Epidemiology</h4><p>Empyemas are usually the complication of another underlying abnormality, and thus demographics will follow those of the primary cause, e.g. pneumonia, sub-diaphragmatic abscess, oesophageal perforation etc...</p><p>Patients with HIV/AIDS are more likely to have pneumonia, and in turn are more likely to develop an empyema, which may occur in over 5% of cases of pneumonia <sup>5</sup>.</p><h4>Clinical presentation</h4><p>Clinical signs and symptoms in isolation are non-specific, and mimic pulmonary infection of any compartment, with fever and increased white cell count being common. In the setting of a pleural collection, consolidation and infective symptoms, imaging alone is unable to exclude infection, and thoracocentesis with microbiological assessment is required. Presence of gas locules within the collection or thickened enhancing pleural margins are strongly indicative of infection (see below).</p><p>Additionally the presumptive diagnosis can be made if the fluid pH is <7.0 or the fluid has glucose level <40mg/dL <sup>4</sup>. </p><h4>Pathology</h4><h5>Microbiology</h5><p>Offending organisms vary somewhat according to the age at which the empyema develops and the underlying abnormality/primary site of infection. For parapneumonic empyemas most frequent organisms are <sup>7,9</sup>:</p><ul>
~~-<li>anaerobic bacteria : usually polymicrobial</li>~~
+<li>anaerobic bacteria: usually polymicrobial</li>
-</ul><p>In the setting of trauma or thoracic surgery <em>staphylococcus aureus</em> is usually involved <sup>10</sup>.</p><h4>Radiographic features</h4><h5>Plain film</h5><p>Can resemble a pleural effusion and can mimic a peripheral pulmonary abscess, although a number of features usually enable distinction between the two (see <a href="/articles/empyema-vs-pulmonary-abscess">empyema vs lung abscess</a>) <sup>3</sup>. Pleural fluid is typically unilateral or markedly asymmetric <sup>4</sup>. Generally empyemas form an obtuse angle with the chest wall, and due to their lenticular shape are much larger in one projection (e.g. frontal) compared to the orthogonal projection (e.g. lateral) <sup>3</sup>. The lenticular shape (bi-convex) is also suggestive of the diagnosis, as transudative / sterile pleural effusions tend to be cresentic in shape (i.e concave towards the lung, see <a href="/articles/empyema-vs-pleural-effusion">empyema vs pleural effusion</a>). </p><h5>Ultrasound</h5><p>The appearances of an empyema depend on the composition of the collection. Typically they are not uniformly anechoic and are often often septated.</p><p>Ultrasound has a major role in enabling targeted thoracocentesis.</p><h5>CT</h5><p>Typically appears as a fluid density collection in the pleural space, sometimes with locules of gas. They form obtuse angles with the adjacent lung, which is displaced and compressed. The pleura is thickened due to fibrin deposition and in-growth of vessels with enhancement. At the margins of the empyema, the pleura can be seen dividing into parietal and visceral layers, the so-called <a href="/articles/split-pleura-sign">split pleura sign</a>, which is the most sensitive and specific sign on CT, and is helpful in distinguishing an empyema from a peripheral <a href="/articles/lung_abscess">lung abscess</a> (see <a href="/articles/empyema-vs-pulmonary-abscess">empyema vs lung abscess</a>) <sup>2-3</sup>. The inner walls of the empyema are smooth.</p><h4>Treatment and prognosis</h4><p>Prompt evacuation of the infected fluid along with appropriate antibiotics is the mainstay of treatment, and will not only improve survival but also hopefully prevent the formation of a <a href="/articles/fibrothorax">fibrothorax</a>.</p><p>Evacuation may be performed with percutaneous chest tube placement often with administration of fibrinolytic agent (e.g. streptokinase or urokinase <sup>8</sup>) into the pleural space to break down septations. Alternatively video-assisted thoracic surgery (VATS), open decortication, or even <a href="/articles/clagett-thoracotomy">Clagett thoracotomy</a> may be performed. VATS is increasingly thought to lead to faster resolution with lower morbidity and reduced cost <sup>5-6</sup>.</p><p>Prognosis is not surprisingly worse in HIV / AIDS patients with reduced CD<sub>4</sub> counts <sup>5</sup>. </p><h5>Trivia</h5><ul><li>Baron Guillaume Dupuytren (of <a href="/articles/dupuytren-contracture">Dupuytren contracture</a> fame) Bonaparte died of an empyema in 1835 <sup>6,7</sup>.</li></ul><h4>Differential diagnosis</h4><p>General imaging differential considerations include</p><ul>
+</ul><p>In the setting of trauma or thoracic surgery <em>staphylococcus aureus</em> is usually involved <sup>7</sup>.</p><h4>Radiographic features</h4><h5>Plain film</h5><p>Can resemble a pleural effusion and can mimic a peripheral pulmonary abscess, although a number of features usually enable distinction between the two (see <a href="/articles/empyema-vs-pulmonary-abscess">empyema vs lung abscess</a>) <sup>3</sup>. Pleural fluid is typically unilateral or markedly asymmetric <sup>4</sup>. Generally empyemas form an obtuse angle with the chest wall, and due to their lenticular shape are much larger in one projection (e.g. frontal) compared to the orthogonal projection (e.g. lateral) <sup>3</sup>. The lenticular shape (bi-convex) is also suggestive of the diagnosis, as transudative/sterile pleural effusions tend to be cresentic in shape (i.e concave towards the lung, see <a href="/articles/empyema-vs-pleural-effusion">empyema vs pleural effusion</a>). </p><h5>Ultrasound</h5><p>The appearances of an empyema depend on the composition of the collection. Typically they are not uniformly anechoic and are often often septated.</p><p>Ultrasound has a major role in enabling targeted thoracocentesis.</p><h5>CT</h5><p>Typically appears as a fluid density collection in the pleural space, sometimes with locules of gas. They form obtuse angles with the adjacent lung, which is displaced and compressed. The pleura is thickened due to fibrin deposition and in-growth of vessels with enhancement. At the margins of the empyema, the pleura can be seen dividing into parietal and visceral layers, the so-called <a href="/articles/split-pleura-sign">split pleura sign</a>, which is the most sensitive and specific sign on CT, and is helpful in distinguishing an empyema from a peripheral <a href="/articles/lung-abscess">lung abscess</a> (see <a href="/articles/empyema-vs-pulmonary-abscess">empyema vs lung abscess</a>) <sup>2-3</sup>. The inner walls of the empyema are smooth.</p><h4>Treatment and prognosis</h4><p>Prompt evacuation of the infected fluid along with appropriate antibiotics is the mainstay of treatment, and will not only improve survival but also hopefully prevent the formation of a <a href="/articles/fibrothorax">fibrothorax</a>.</p><p>Evacuation may be performed with percutaneous chest tube placement often with administration of fibrinolytic agent (e.g. streptokinase or urokinase <sup>8</sup>) into the pleural space to break down septations. Alternatively video-assisted thoracic surgery (VATS), open decortication, or even <a href="/articles/clagett-thoracotomy">Clagett thoracotomy</a> may be performed. VATS is increasingly thought to lead to faster resolution with lower morbidity and reduced cost <sup>5-6</sup>.</p><p>Prognosis is not surprisingly worse in HIV/AIDS patients with reduced CD<sub>4</sub> counts <sup>5</sup>. </p><h5>Trivia</h5><ul><li>Baron Guillaume Dupuytren (of <a href="/articles/dupuytren-contracture">Dupuytren contracture</a> fame) Bonaparte died of an empyema in 1835 <sup>6</sup>.</li></ul><h4>Differential diagnosis</h4><p>General imaging differential considerations include</p><ul>
~~-<a href="/articles/lung_abscess">lung abscess - </a>see<a href="/articles/lung_abscess"> </a><a href="/articles/empyema-vs-pulmonary-abscess">empyema vs lung abscess</a>~~
+<a href="/articles/lung-abscess">lung abscess</a>: see<a href="/articles/lung-abscess"> </a><a href="/articles/empyema-vs-pulmonary-abscess">empyema vs lung abscess</a>
~~-<a href="/articles/pyopneumothorax">pyopneumothorax</a> - can be thought of a sub type of a empyema</li></ul>~~
+<a href="/articles/pyopneumothorax">pyopneumothorax</a>: can be thought of a sub type of a empyema</li></ul>

References changed:

7. Sherwood L. Gorbach, John G. Bartlett, Neil R. Blacklow. Infectious Diseases. (2004) ISBN: 9780781733717 - <a href="http://books.google.com/books?vid=ISBN9780781733717">Google Books</a>
10. Gorbach SL, Bartlett JG, Blacklow NR. Infectious diseases. Lippincott Williams & Wilkins. (2004) ISBN:0781733715. <a href="http://books.google.com/books?vid=ISBN0781733715">Read it at Google Books</a> - <a href="http://www.amazon.com/gp/product/0781733715?ie=UTF8&tag=radiopaediaor-20&linkCode=as2&camp=1789&creative=9325&creativeASIN=0781733715">Find it at Amazon</a><div class="ref_v2"></div>
7. Baron Guillaume Dupuytren from whonamedit.com, the dictionary of medical eponyms. <a href="http://www.whonamedit.com/doctor.cfm/1104.html">Baron Guillaume Dupuytren</a><div class="ref_v2"></div>

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