AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

Background

A lung abscess is a subacute infection in which an area of necrosis forms in the lung parenchyma. It usually is in a dependent section of the lung, more often involves the right lung than the left, and is most commonly seen after aspiration of oropharyngeal secretions. Lung abscesses have a slow, insidious presentation and usually develop 1-2 weeks after the initial aspiration event.

Empyema is defined as pus in the pleural space. It typically is a complication of pneumonia. However, it can also arise from penetrating chest trauma, esophageal rupture, complication from lung surgery, or inoculation of the pleural cavity after thoracentesis or chest tube placement. An empyema can also occur from extension of a subdiaphragmatic or paravertebral abscess.

Pathophysiology

A lung abscess involves the lung parenchyma, while an empyema involves the pleural space. In many patients with pneumonia, a sterile simple parapneumonic effusion develops in the pleural space. If this pleural effusion becomes infected, it is labeled a complicated parapneumonic effusion, while the presence of frank pus in the pleural space defines an empyema. The development stages of an effusion can be divided into 3 phases: exudative, fibropurulent, and organizational. The initial effusion develops from increased pulmonary interstitial fluid along with progressive capillary vascular permeability. A simple effusion is frequently sterile and resolves with antibiotic treatment of the underlying pulmonary infection. In 5-10% of the patients with a pleural effusion, the effusion becomes infected and neutrophils buildup. This inflammatory response also causes the production of chemokines, cytokines, oxidants, and protease mediators. This more complicated parapneumonic effusion needs both antibiotics and some form of surgical drainage or alternative treatment modality to remove the purulent effusion. In these more complicated effusions, fibrinolysis and activation of the coagulation cascade leads to the production of fibrin with subsequent adhesions and loculated fluid collections. This process ultimately can cause pleural fibrosis and impairment of lung expansion.

Frequency

United States

An estimated 60,000 pleural infections are diagnosed annually in the United States.

Mortality/Morbidity

The mortality rate for lung abscesses is approximately 4-7% but varies with the type of material aspirated. Aspiration of fluids with mixed gram-negative flora has a mortality rate approaching 20%, while aspiration of acidic materials has an even higher rate. The fatality rate for complicated parapneumonic effusions is estimated to be as high as 15%.

Age

Complicated effusions and empyema are more common in elderly persons and during childhood. An increase has occurred in the incidence of empyema in the pediatric population. Lung abscess is more common in elderly persons.

CLINICAL

Section 3 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

History

The patient's history may reveal the following findings:

• Recent diagnosis and treatment of pneumonia
• Recent history of penetrating chest trauma (should raise clinical suspicion for empyema)
• Cough productive of bloody sputum that frequently has a fetid odor or offensive appearance
• Fever
• Shortness of breath
• Anorexia, weight loss
• Night sweats
• Pleuritic chest pain

Physical

The physical examination may reveal the following findings:

• Temperature frequently elevated but usually not greater than 102°F
• Tachypnea
• Rales
• Rhonchi
• Egophony
• Tubular breath sounds
• Decreased breath sounds
• Dullness to percussion

Causes

• The most common cause of lung abscess is aspiration. Patients at the highest risk are those who have the following:
• • Poor dentition
  • Seizure disorder
  • Alcohol abuse
  • Inability to protect their airway because of an absent gag reflex (eg, patients who are comatose, have a change in mentation, or who might be undergoing general anesthesia)
  • Primary lung disorders, such as septic emboli, vasculitic disorders, cavitating lung malignancies, or pulmonary cystic disease
  • Penetrating chest trauma
• The microbiologic organisms involved in lung abscesses typically are polymicrobial oral flora, including Bacteroides, Fusobacterium, and Peptostreptococcus species. Other organisms include Pseudomonas species, Klebsiella species, Staphylococcus aureus, Streptococcus pneumoniae, Nocardia species, and less commonly fungi.
• The most common cause of an empyema is from a parapneumonic effusion that becomes infected; these account for about half of all empyemas. Other causes of an empyema include the following:
• • Penetrating chest trauma 
  • Contamination of a wound because of inadequate skin preparation during procedures such as needle decompression, chest tube placement, thoracentesis, or lung surgery
• Microbiologic organisms that cause an empyema include streptococcus species such as Streptococcus intermedius, Streptococcus constellatus, Streptococcus inonia, S pneumoniae, staphylococci, and a variety of gram-negative organisms and anaerobes. In the pediatric population, S aureus has become the predominant organism associated with empyemas because of the widespread use of the pneumococcal conjugate vaccine. One should always consider methicillin-resistant Staphylococcus aureus (MRSA), enterobacteria, enterococcus, and Mycobacterium tuberculosis as potential pathogens.

DIFFERENTIALS

Section 4 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

Other Problems to be Considered

Sarcoidosis

WORKUP

Section 5 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

Lab Studies

• A CBC with differential may reveal a leukocytosis and a left shift.
• Collect sputum for Gram staining, culturing, and sensitivity testing.
• If tuberculosis is suspected, acid-fast bacilli testing should be obtained.
• Blood culturing is also appropriate.

Imaging Studies

• Perform chest radiography to diagnose and differentiate pneumonia, pulmonary abscess, and empyema. Distinction of these conditions is important because lung abscesses and pneumonia require medical treatment, while empyema frequently requires definitive surgical therapy.
• On the chest radiograph, a lung abscess appears as a solitary cavitary area with an air-fluid level, which typically is present in a dependent portion of the lung.
• A surrounding patchy area of infiltrate aids in differentiating a pulmonary abscess from a cavitary lung cancer.
• On the chest radiograph, findings that suggest empyema, as opposed to lung abscess, include extension of the air-fluid level to the chest wall, extension of the air-fluid level across fissure lines, and a tapering border of the air-fluid collection.
• The costophrenic angle should be closely inspected on the chest radiograph to assess the presence of fluid that suggests effusion or empyema.
• On the chest radiograph obtained of the patient in an upright position, blunting of the costophrenic angle occurs when approximately 200 mL of fluid accumulates.
• A lateral chest decubitus radiograph, obtained with the patient on his or her side, reveals whether the pleural fluid is mobile and forms layers or whether it is loculated.
• To better assess any abnormal lung findings found on a chest radiograph, CT of the chest or ultrasonography is required. Ultrasonography is useful for needle-guided aspiration and drainage of a potential pleural effusion. When ultrasonography is not used to guide needle aspiration, the failure rate is 12-15%. CT of the chest can assess for pneumonia, lung abscess, tumor, pleural effusions and septations, other pleural diseases, or pleural thickening.

Other Tests

• Pulse oximetry - To assess oxygenation
• ABG analysis - To assess respiratory adequacy
• Transtracheal aspiration for culturing - If sputum findings are nondiagnostic

Procedures

• If a pleural effusion is present, a diagnostic thoracentesis should be performed, and the fluid should be analyzed for pH, lactate dehydrogenase, and glucose levels; specific gravity; and cell count with differential. Fluid is also sent for Gram stain, culture, and sensitivity.
• Gram stain, routine culture, and sensitivity, and acid-fast bacillus testing should also be performed.
• The fluid should be sent for cytology if cancer is suspected.
• The following findings are suggestive of an empyema or parapneumonic effusion that will need a chest tube for complete resolution:
• • Grossly purulent pleural fluid
  • pH level less than 7.2
  • WBC count greater than 50,000 cells/µL (or polymorphonuclear leukocyte count of 1,000 IU/dL)
  • Glucose level less than 60 mg/dL
  • Lactate dehydrogenase level greater than 1,000 IU/mL
  • Positive pleural fluid culture
• A pleural fluid marker currently being studied is tumor necrosis factor (TNF)–alpha. In patients who have pleural effusions, a TNF-alpha level higher than 80 pg/mL is suggestive of an empyema or complicated parapneumonic effusion.

TREATMENT

Section 6 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

Prehospital Care

• Supplemental oxygen should be given and an intravenous line started.
• Appropriate airway management, including intubation, should be performed depending on the patient's clinical condition.

Emergency Department Care

• All patients should undergo pulse oximetry and evaluation of their respiratory status.
• • If respiratory failure is found or likely to occur, intubation and mechanical ventilation is necessary.
  • Supplemental oxygen should be started for any patient who is acutely short of breath or who is hypoxic based on pulse oximetric findings.
• Once the diagnosis of a lung abscess is made, parenteral antibiotics should be started. Ideally, sputum and blood culture findings should be obtained prior to the initiation of antibiotics.
• After the diagnosis of empyema is made, prompt drainage by means of tube thoracostomy with use of parenteral antibiotics should be initiated.

Consultations

Treatment of lung abscesses or empyema is performed in-hospital, with consultations involving internists, thoracic surgeons, or both. Many clinicians advocate administering intrapleural fibrinolytics in patients with empyemas to assist in the breakdown of fibrin bands that can cause loculation of the empyema and to allow for better chest tube drainage of the infected material. However, randomized clinical trials have given conflicting results about the benefits of fibrinolytic therapy on outcomes. A recent meta-analysis that included 575 patients showed no benefit for the use of fibrinolytic therapy based on clinical outcomes of death or need for surgery when compared with control groups. If chest tube drainage and fibrinolytic treatment are unsuccessful, many authors recommend video-assisted thoracic surgery (VATS) rather than the more traditional open thoracotomy. VATS is less invasive and well tolerated, and outcomes compare favorably with open thoracotomy.

In the pediatric population, Avansino et al performed a meta-analysis comparing nonoperative (antibiotics and either thoracentesis and/or tube thoracostomy) with operative therapy (antibiotics and either VATS or thoracotomy) in patients with an empyema.¹ Their results suggest that, with operative therapy, the in-hospital mortality rate, reintervention rate, length of stay, time with tube thoracostomy, and time of antibiotic therapy are lower compared with nonoperative treatment. 

Lung abscesses typically respond well to antibiotic therapy, but when that therapy is unsuccessful, the consulting clinician might consider percutaneous catheter drainage or endoscopic surgical resection of the involved area of the lung.

MEDICATION

Section 7 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

Lung abscesses are treated with a prolonged course of parenteral antibiotics that target organisms found in aspiration pneumonia. The initial choice of antibiotics frequently is empiric, beginning with clindamycin, cefoxitin, ticarcillin, or piperacillin/tazobactam, although penicillin has been very effective when the organism is sensitive. Some authors advocate adding coverage for Klebsiella as well. Subsequent therapy should be based on sputum or blood culture results.

An empyema is treated with parenteral antibiotics and prompt chest tube drainage. Empiric therapy for an empyema is frequently with imipenem or piperacillin/tazobactam until a definitive organism is identified on pleural fluid cultures and sensitivities are obtained. Antibiotic coverage for anaerobic organisms is also recommended since anaerobes frequently coexist but are more difficult to isolate. For an empyema secondary to aspiration pneumonia or a parapneumonic process, choose antibiotics that are active against mouth flora, S aureus and Streptococcus species. For an empyema secondary to penetrating chest trauma, administer antibiotics that have coverage for skin flora. If MRSA is suspected, include vancomycin in the treatment plan. Pleural fluids or sputum specimens that are obtained should be cultured for M tuberculosis as well.

Drug Category: Antibiotics

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.

FOLLOW-UP

Section 8 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

Further Inpatient Care

• Inpatient care is mandatory for the management and assistance of the patient's respiratory status, continuation of intravenous antibiotics, and drainage of the abscess or empyema as needed.

In/Out Patient Meds

• Outpatient therapy for these conditions is not indicated or advised; inpatient care is mandatory.
• Antimicrobial therapy should be continued empirically until therapy can be guided with culture results.

Transfer

• Transfer of these patients usually is not indicated unless advanced respiratory management or surgical drainage is not available without transfer.
• Patients should be transferred only after stabilization of their respiratory status and administration of intravenous antibiotics.

Deterrence/Prevention

• Prevention of aspiration is important to minimize the subsequent risk of lung abscess.
• Early intubation should be performed in patients who do not have a gag reflex.
• Position the patient in a manner that minimizes the risk of aspiration. For example, a patient who is vomiting should be placed on his or her side.
• Immediately suction the patient's orotracheal area if he or she aspirates in the ED.

Complications

• Complications of pulmonary abscess include pleural fibrosis, trapped lung, restrictive ventilatory defect, bronchopleural fistula, and pleurocutaneous fistula.

Prognosis

• The prognosis for both lung abscess and empyema generally is good. Ninety percent of lung abscesses are cured with medical management alone.

Patient Education

• For excellent patient education resources, visit eMedicine's Infections Center, Lung and Airway Center, and Pneumonia Center. Also, see eMedicine's patient education articles Bacterial Pneumonia, Abscess, and Antibiotics.

MISCELLANEOUS

Section 9 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

Medical/Legal Pitfalls

• Failure to suspect the diagnosis
• Failure to perform thoracentesis for a pleural effusion: The fluid results assist in the treatment of the patient by allowing differentiation of an empyema and parapneumonic effusion. Empyema requires chest tube placement while a simple parapneumonic effusion can be treated with intravenous antibiotics alone.

ACKNOWLEDGMENTS

Section 10 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

The authors and editors of eMedicine gratefully acknowledge the contributions of previous author, Patti Purpura, MD, to the development and writing of this article.

REFERENCES

Section 11 of 11

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Acknowledgments
• References

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Article Last Updated: Nov 7, 2007