Lung Abscess

A lung abscess is a lung infection accompanied by pus accumulation and tissue destruction. The abscess may be putrid (due to anaerobic bacteria) or non­putrid (due to anaerobes or aerobes), and often has a well-defined border. The availability of effective antibiotics has made lung abscesses much less common than they were in the past.

Causes

A lung abscess is a manifestation of necrotizing pneumonia, often the result of aspiration of oropharyngeal contents. Poor oral hygiene with dental or gingival (gum) disease is strongly associated with a putrid lung abscess. Septic pulmonary emboli commonly produce cavitary lesions. Infected cystic lung lesions and cavitating bronchial carcinoma must be distinguished from lung abscesses.

Signs and symptoms

The symptoms may start slowly or suddenly. Early symptoms resemble those of pneumonia: fatigue, loss of appetite, sweating, fever, and a cough that brings up sputum. The sputum may be foul smelling (because certain bacteria from the mouth or throat tend to produce foul odors) or streaked with blood. The person also may feel chest pain with breathing, especially if the pleura is inflamed. Many people have these symptoms for weeks or months before seeking medical attention. These people have chronic abscesses and, in addition to the other symptoms, lose a substantial amount of weight, have a fever every day, and also have night sweats.

Diagnosis

The following tests are used to diagnose a lung abscess:

• Auscultation of the chest may reveal crackles and decreased breath sounds.
• Chest X-ray shows a localized infiltrate with one or more clear spaces, usually containing air-fluid levels.
• Chest CT Scan
• Thoracentesis (scope passed into lungs) or needle biopsy, if diagnosis is unclear

Treatment

Antibiotic therapy often lasts for months until radiographic resolution or definite stability occurs. Symptoms usually disappear in a few weeks. Postural drainage may facilitate discharge of necrotic material into upper airways, where expectoration is possible; oxygen therapy may relieve hypoxemia. A poor response to therapy requires resection of the lesion or removal of the diseased section of the lung. All patients need rigorous follow-up and serial chest X-rays.

About 5% of people with lung abscesses need additional treatment. Occasionally, an abscess requires drainage through a tube inserted through the chest wall and into the abscess. More often, infected lung tissue may have to be removed surgically. Sometimes an entire lobe of a lung or even an entire lung has to be removed.

The death rate for people with lung abscesses is about 5%. The rate is higher when the person is debilitated or has an impaired immune system, lung cancer, or a very large abscess.

Prevention

Some of the conditions that make people more vulnerable to lung abscess concern long-term lifestyle behaviors, such as substance abuse and lack of dental care. Others, however, are connected with chronic illness and hospitalization. Aspiration can be prevented with proper care of unconscious patients, which includes suctioning of throat secretions and positioning patients to promote drainage. Patients who are conscious can be given physical therapy to help them cough up material in their lungs and airways. Patients with weakened immune systems can be isolated from patients with pneumonia or fungal infections.