An abscess of the lung is a cavity filled with pus encircled by inflamed tissue that is typically caused by infection. Lung abscesses can be caused by a variety of bacteria and other microorganisms, many of which inhabit the mouth and throat and can be inhaled into the lungs.

In most individuals, such bacteria are inhibited in their migration toward the lungs by the body’s natural defenses, such as coughing and the gag reflex. People whose airway defense mechanisms are hindered, such as those who are sedated or unconscious, are at elevated risk of developing lung abscesses.

The bacterium Staphylococcus aureus is one of the many microorganisms that can cause lung abscesses. Staphylococci are Gram-positive anaerobes that characteristically aggregate into clusters reminiscent of grapes. Sometimes S. aureus first leads to pneumonia before resulting in complications, including abscess formation. S. aureus can also result in abscesses via other means. For instance, intravenous drug users can transmit the microorganism via the blood, which often results in multiple abscesses in various parts of the lungs. Abscesses involving S. aureus can be difficult to cure because the bacterium is resistant to many antibiotic medications. Consequently, sensitivity tests are often utilized to determine the best drug available to treat particular strains of the microorganisms.

The spread of the pus contained in an abscess can cause bronchopneumonia and acute respiratory distress syndrome. By administering antibiotics in a timely manner, rupture and further dissemination of infection can often be avoided. Accordingly, patients should quickly seek medical attention when they notice the symptoms of a lung abscess, which may develop acutely or gradually. Signs of the condition frequently include fever, night sweats, malaise, appetite loss, and coughing up sputum. The sputum associated with a lung abscess may be streaked with blood or have a foul odor, especially if the causative organism is an anaerobic bacterium, such as Staphylococcus aureus.

Most abscesses can be identified in a chest x-ray, though sometimes computed tomography (CT) scans are necessary. CT scans can also sometimes provide information regarding the cause of the condition. In other cases, sputum smears and cultures can be helpful in determining the cause of an abscess. However, because of the microorganisms that are normally present in the mouth and throat, expectorated sputum is not useful for analyses, so that samples must be obtained via specialized techniques. As a result, some sputum tests are often not carried out unless traditional abscess treatments are ineffective.

The majority of lung abscesses can be cured over the course of several weeks with a regimen of antibiotics. Medications are often initially administered intravenously and then provided in an oral form once fever and other serious symptoms of the condition are adequately alleviated. Approximately five to ten percent of lung abscess cases require additional or alternative treatment. Surgery is necessary for patients with abscesses caused by a foreign object or tumor blockage of the airways.

Lung Abscess at 20x Magnification - Factors that can increase risk of developing a lung abscess include poor dental hygiene and periodontal disease, alcohol abuse, and various lung disorders, including pneumonia.

Lung Abscess at 10x Magnification - Over time, most lung abscesses rupture, emptying their contents into one of the bronchi, from which it can be coughed up, or into the pleural cavity, resulting in what is known as empyema.

Lung Abscess at 40x Magnification - Since the symptoms of a lung abscess are similar to pneumonia and other lung disorders, testing must be carried out to produce a definitive diagnosis.

Lung Abscess at 20x Magnification - A lung abscess may be drained through a tube inserted through the chest or part of the lung tissue may be removed, primarily when caused by a microorganism that does not respond to antibiotics.