pulmonary disorders
Lung Abscess
Diagnosis of Lung Abscess
Chest x-ray Often chest CT for better visualization or if endobronchial obstruction is suspected Sputum cultures for aerobic bacteria, fungi, and mycobacteria Bronchoscopy as needed to exclude cancer, detect unusual pathogens such as fungi or mycobacteria, and in immunocompromised patients Culture of any pleural fluid Lung abscess is suspected based on history in a patient who is at risk (eg, aspiration-prone due to altered consciousness or dysphagia or who is immunosuppressed) and is confirmed by chest x-ray showing cavitation. Cavitary pulmonary lesions are not always caused by infection. Noninfectious causes of cavitary pulmonary lesions include the following: Empyema or bulla with air-fluid level Cystic (saccular) Bronchiectasis None Lung Carcinoma None Lung infarction Nodular Silicosis nodule with central necrosis Pulmonary Embolism (PE) None Pulmonary sequestration Sarcoidosis None Granulomatosis with Polyangiitis (GPA) None Extra-articular manifestations None In an anaerobic infection due to aspiration, chest x-ray classically shows consolidation with a single cavity containing an air-fluid level in portions of the lung that would be dependent when the patient is recumbent (eg, the posterior segments of the upper lobes or the superior or lateral basal segments of the lower lobes). This pattern helps distinguish anaerobic abscess from other causes of cavitary pulmonary disease, because diffuse or embolic pulmonary disease often causes multiple cavitations, and tuberculosis typically involves the apices. CT is not routinely needed (eg, if cavitation is clear on chest x-ray in a patient who has risk factors for lung abscess). However, CT may be useful when cavitation is suggested but not clearly seen on the chest x-ray, when an underlying pulmonary mass obstructing the drainage of a lung segment is suspected, or when abscess needs to be differentiated from empyema or bulla with an air-fluid level. Lung Carcinoma can lead to obstruction that causes pneumonia and abscess formation. Bronchial carcinoma should be suspected in patients who do not respond to antimicrobial treatment or have atypical findings such as a cavitary lesion and no fever. Bronchoscopy is sometimes done to exclude cancer or the presence of a foreign body or to detect unusual pathogens, such as fungi or mycobacteria. Bronchoscopy is done if patients are immunocompromised. Anaerobic bacteria are rarely identifiable on culture because uncontaminated specimens are difficult to obtain and because most laboratories do not culture anaerobes well or often. If sputum is putrid, then anaerobic infection is assumed to be the cause. However, if empyema is present, pleural fluid provides a good source for anaerobic culture. When clinical findings make anaerobic infection less likely, aerobic, fungal, or mycobacterial infection should be suspected, and attempts should be made to identify a pathogen. Cultures of sputum, bronchoscopic aspirates, or both are helpful. 