Lung Abscess - A Brief Discussion

A lung abscess is an infection accompanied by pus accumulation and tissue destruction. The abscess may be putrid (due to anaerobic bacteria) or non putrid (due to anaerobes or aerobes), and it commonly 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, commonly 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
Signs and symptoms of lung abscess include a cough that may produce bloody, purulent, or foul-smelling sputum; pleuritic chest pain; dyspnea; excessive sweating; chills; fever; headache; malaise; diaphoresis; and weight loss.

Complications include rupture into the pleural space, which results in empyema and, rarely, massive hemorrhage. A chronic lung abscess may cause localized bronchiectasis. Failure of an abscess to improve with antibiotic treatment suggests a possible underlying neoplasm or another cause of obstruction.

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 computed tomography scan confirms the presence of localized infiltrate or nodular density, occasionally with air-fluid level. Chest imaging may also identify airway masses or foreign bodies that have led to abscess formation.
• Percutaneous aspiration of an abscess or bronchoscopy may be used to obtain cultures to identify the causative organism. Bronchoscopy is only used if abscess resolution is eventful and the patient’s condition permits it.
• Blood cultures, Gram stain, and sputum culture are also used to detect the causative organism.
• White blood cell count commonly exceeds 10,000/µl.

Treatment
Antibiotic therapy may last 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.