Empyema

An empyema should be suspected in patients with pulmonary infection if there is persisting or recurrent pyrexia despite treatment with a suitable antibiotic. Patients with empyema due to aerobic bacterial infection usually have high and remittent pyrexia, rigors, sweating, malaise and weight loss. Blood counts show polymorphonuclear leukocytosis and high C-reactive protein. Locally, there is pleural pain, breathlessness, cough and sputum. Empyema with anaerobic bacterial infections involving the pleural space presents with a subacute illness with symptoms for more than 7 days.

Low grade fever, weight loss and anemia is commonly seen. Clinical signs of pleural effusion are present such as decreased or absent breath sounds, dull notes on percussion, a decreased tactile fremitus. Large pleural effusions may show an evidence of tension and contralateral tracheal shift [6].

• Blood: Leukocytosis is present, and should decrease with treatment.
• Sputum culture: Gram stain may often show the causative organism.
• Chest radiographs: Evidence of pleural fluid is present. In pyopneumothorax an air-fluid level is observed.
• Ultrasonography: Shows the position of the fluid, the extent of pleural thickening and whether fluid is in a single collection or multiloculated by fibrin and debris, helps in thoracocentesis in loculated pleural effusions. 
• Computed tomography (CT) scan: CT gives information on the pleura, the underlying lung parenchyma and patency of the major bronchi. CT of the chest with contrast assists in delineating the pleural fluid loculations. 
• Aspiration of fluid: Ultrasound or CT is used to identify the optimal site to undertake aspiration, which is best performed using a wide-bore needle. If the fluid is thick and turbid pus, empyema is confirmed. Other features suggesting empyema are a fluid glucose < 40 mg/dL), LDH > 1000 U/L or a fluid pH < 7.0. Pleural fluid studies include blood cell count and differential blood cell counts. WBC counts are generally greater than 50,000 cells/µL. 
• Microbiology: Gram stain and bacterial culture may be done but antibiotic treatment may render all fluids sterile. The distinction between tuberculous and nontuberculous disease can be difficult and often requires pleural biopsy, histology and culture. 

An empyema will only heal if infection is eradicated and the empyema space is obliterated, allowing apposition of the visceral and parietal pleural layers.

Treatment of non-tuberculous empyema

• Drainage: When the patient is acutely ill and the pus is sufficiently thin, a wide-bore intercostal tube should be inserted into the most dependent part of the empyema space (using ultrasound or CT guidance in difficult cases) and connected to an underwater-seal drain system. If the initial aspirate reveals turbid fluid or frank pus, or if loculations are seen on ultrasound, the tube should be put on suction (-5 to -10 cm of water) and flushed regularly with 20 mL normal saline. 
• Fibrinolytics: Intrapleural streptokinase or urokinase is given in case of loculations [7]. 
• Surgery: Video-assisted thoracoscopic surgery (VATS) and surgery when the pus is thick or loculated. Thickened pleura in some cases might need surgical "decoration".
• Antibiotics: An antibiotic directed against the organism causing the empyema should be given for 2-4 weeks. For a patient with community-acquired pneumonia, a second or third generation cephalosporin in combination with a macrolide needs to be given. For patients hospitalized with severe community-acquired pneumonia, a macrolide plus a third-generation cephalosporin with antipseudomonal activity is required [8] [9]. 

Treatment of tuberculous empyema

Immediate initiation of antitubercular chemotherapy is essential. The pus in the pleural space is aspirated through a wide-bore needle with intercostal tube drainage if necessary until the pus ceases to reaccumulate. Surgery is occasionally required to ablate a residual empyema space.

Mortality rate from empyema is higher in the presence of cardiac and respiratory comorbidities, immunosuppressive states and old age. Surgical procedures including decortication and/or an open drainage procedure are required in 15-25% of patients. Fibrothorax with restriction and encasement of the lung in thickened, often calcified pleura, is a late complication in tuberculous empyema. Death rates are estimated to be approximately 10% [5].

70% of empyema thoracis are caused by bacterial pneumonia. 30% cases arise as complications of previous cardiothoracic surgery, in which case Staphylococcus aureus is the most common bacteria. Apart from surgery, empyema may arise with the bacterial spread locally or through blood such as from esophageal perforation or septicemia. Streptococcus pneumoniae and Staphylococcus aureus account for nearly 70% of aerobic gram-positive cultures isolated in empyema. Aerobic gram-negative organisms are mainly Klebsiella, Pseudomonas and Hemophilus species [2].

In the United States, approximately 500,000 to 750,000 patients are diagnosed with parapneumonic effusions per year- of which nearly 5 to 10% require a drainage or surgical procedure. Children, elderly and debilitated persons are at a higher risk for developing empyema. Other risk factors include pneumonia requiring hospitalization and coexisting diseases like rheumatoid arthritis, bronchiectasis, diabetes mellitus, alcoholism and gastroesophageal reflux disease. Chalmers et al identified 7 clinical factors that predict the development of empyema: an albumin value of less than 30 g/L, a platelet count of greater than 400,000,000,000/L, a C-reactive protein level of greater than 100 mg/L, a serum sodium value of less than 130 mmol/L, and a history of intravenous drug or alcohol abuse. A decreased risk was found in a history of chronic obstructive pulmonary disease [3].

5 to 10 days after the onset of pneumonia, bacterial invasion of the pleural space occurs leading to the accumulation of polymorphonuclear leukocytes, bacteria, and cellular debris in the form of a thick inflammatory exudate in the pleural space. The pleural fluid may test positive for microorganisms. The pus in the pleural space is often under considerable pressure and if the condition is not adequately treated, pus may rupture into a bronchus causing a bronchopleural fistula and pyopneumothorax or track through the chest wall with the formation of a subcutaneous abscess or sinus (termed empyema necessitans). Loculation and septation may occur [4].

Early diagnosis and treatment of bacterial pneumonias can prevent many cases of empyema, especially in high risk cases. Early diagnosis and drainage may obviate the need for surgical treatment in established cases of empyema [10].

An empyema is a collection of pus within an anatomical cavity. The condition may occur for example in the uterus, the appendix or the gallbladder. Usually, the term refers to thoracic empyema which is mostly caused by bacterial invasion of the pleural space. It may present with acute symptoms of fever, chest pain and sputum in case of aerobic infections; or a more indolent subacute febrile illness with weight loss in anaerobic infections.

Clinically, empyema is characterized by decreased or absent breath sounds and dullness on percussion. Complete blood counts, microbiological analysis of sputum or pleural fluid, imaging studies of chest and ultrasound are used for diagnosis. Treatment modalities include pleural drainage, surgery, broad spectrum antibiotics and infusion of intrapleural thrombolytic agents. Mortality rates are around 10% [1].

Empyema is a collection of pus inside the thin space between the inner lining of your chest wall and the surface of the lungs. Most commonly, empyema results as a complication of pneumonia or lung abscess. Sometimes it may happen after a surgery on the chest. The patients have fever, cough, shortness of breath, and chest pain that increases on breathing or movement of chest. They may have a low grade fever, loss of appetite and weight loss in some infections. Antibiotics to treat the bacterial infection and medications for the fever are given to treat this condition. The pus is drained using chest tube to allow the lungs to expand normally. 

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8. [Guideline] Colice GL, Curtis A, Deslauriers J, et al. Medical and surgical treatment of parapneumonic effusions : an evidence-based guideline. Chest. Oct 2000;118(4):1158-71. 
9. [Guideline] Mandell LA, Wunderink RG, Anzueto A, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis. Mar 1 2007;44 Suppl 2:S27-72
10. Mandal AK, Thadepalli H, Mandal AK, Chettipally U. Outcome of primary empyema thoracis: therapeutic and microbiologic aspects. Ann Thorac Surg 1998; 66:1782.

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