A lung abscess is a pocket of necrotized lung tissue. Microorganisms such as bacteria, fungus, and parasites can infect lung tissue. The tissue dies and turns into a liquefied mix of dead matter and white blood cells or pus. Lung abscesses were fatal in 75% of all cases before the discovery of antibiotics. Access to modern medical care has increased the recovery rate to more than 90%, but lung infections are still life-threatening.
Primary lung abscesses account for 60% of all cases, and aspiration — breathing food particles into the trachea instead of the esophagus — is the most common cause. Bacteria on the particles enter the lungs, which lack the stomach acid that would kill them if normally ingested. Other common causes include sinus infections, infections in the teeth and gums, pneumonia, frequent vomiting, and acid reflux. Like food, stomach acid in the esophagus or mouth can enter the trachea and damage lung tissue.
Secondary lung abscesses account for the remaining cases and are so named because they occur as a result of another issue. Obstructions in the bronchial tubes that branch out from the trachea are one such cause. Others include COPD, tuberculosis, emphysema, cystic fibrosis, and infections in the abdomen or other organs. Lung injuries can cause abscesses, as well. Contusions occur when blunt force trauma affects the lungs, as can happen in car accidents and serious falls. Tumors and enlarged lymph nodes cause lung abscesses when they obstruct or put too much pressure on surrounding lung tissue.
The early symptoms of a lung abscess are very similar to the symptoms of pneumonia: fever, shivering, night sweats, difficulty breathing, weight loss, fatigue, chest pain, and anemia. Coughing will initially be non-productive, but begin to bring up infected tissues and mucus as the abscess grows. Sometimes, mucus contains noticeable streaks of blood; chronic abscesses, those that last longer than six weeks, can cause foul-smelling expectorations. Lung abscesses may also cause a blue tinge around the lips and fingernails due to insufficient oxygen.
The elderly and people with compromised immune systems have the highest risk of developing lung abscesses. Intubation and mechanical ventilation can push bacteria into the lungs or damage tissues. Anything that causes an altered state of consciousness, such as anesthesia, alcohol, drugs, or injury, can increase risk as well. Aspiration occurs more frequently when people are unconscious or semi-conscious.
Doctors diagnose lung abscesses with a physical examination, lab tests, and soft tissue scans. These tests will highlight diminished or "dull" lung sounds. Foul-smelling sputum indicates a bacterial or fungal infection, and X-rays and CT scans will show cavities filled with fluid or pockets of air. The latter are left behind when an abscess ruptures. Doctors may also use a bronchoscope, a tube with a light and camera that lets doctors retrieve sputum or tissue samples and view the inside of the lungs.
Anaerobic bacteria cause most lung abscesses. These microorganisms do not require oxygen and remain confined in the abscess, which means they do not appear on a blood or sputum culture. Doctors cannot always identify specific bacteria unless the abscess ruptures. Several types of aerobic bacteria cause lung infections, too, and a single abscess may contain multiple strains. Treatment is a combination of at least two broad-spectrum antibiotics; the doctor will alter the prescription as needed to ensure they remain effective.
Chronic or large lung abscesses rarely heal with antibiotics alone. Doctors drain fluid from abscesses with surgery or chest tubes, which remain in place for around two weeks. Endoscopic drainage is an alternative procedure, using a laser, best suited for people in frail health who would could not tolerate surgery or chest tubes. A significant drawback of endoscopic drainage is the possibility of spreading infected tissue and fluid throughout the lung.
Supporting measures to help people recover include high-calorie diets, managing electrolytes and fluid, respiratory therapy, and postural drainage. Respiratory therapists provide supportive cushions or devices and prop patients in such a way that gravity can drain fluid from the lungs. Therapists encourage patients to practice deep breathing exercises to prevent mucus build-up and expel infected fluid and tissue from the lungs.
Empyema is a serious complication that occurs when a lung abscess grows through the lining around the lungs and into the space between the lungs and chest wall. Infected fluid and pus fill the space and may create enough pressure to collapse the lung. A bronchopleural fistula is a connection between airways and the space in the lining around the lungs. Both complications give the infection a route to spread through the abdominal cavity and into the bloodstream.
Fungal infections are rare and often isolated to specific geographic regions. People in poor health with weakened immune systems have the highest risk of developing such infections. Antifungal agents can cause severe side effects and reach toxic levels quickly. Some lung abscesses caused by fungal infections heal within a month, but excessively virulent strains may require up to two years of treatment. The recovery rate for fungal lung abscesses is between 45% to 60%, which is significantly lower than the overall 90% recovery rate.
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