Monitoring
Serial chest x-rays are used to monitor therapeutic response. Cavity closure takes a median time of 4 weeks, but in some cases, may take months.[67] Resolution of surrounding infiltrates requires at least 8 weeks. It is important to note that the chest x-ray appearance may worsen during the first week of treatment and that radiographic improvement may lag behind clinical resolution.[68]
Other monitoring approaches have been recommended. For example, monitoring for a fall in CRP levels is plausible for assessing therapeutic response, but published data are scarce and limited to lung abscesses complicating pneumonia. Albumin may also be low at presentation, particularly with sub-acute or chronic abscesses, but it is not useful for monitoring acute response to antibiotics because its interpretation is affected by confounding conditions. Nevertheless, low albumin appears to predict adverse outcomes and may predispose to the development of infection.[69]
Effective antimicrobial therapy generally leads to a gradual reduction of fever over 7 to 10 days and to a subjective improvement in the patient. Persistent fever beyond 2 weeks raises the suspicion of complications (e.g., empyema), an underlying obstruction (malignancy or foreign body), infection with a resistant organism, or inadequate response to treatment (e.g., with a large cavity). These cases require additional diagnostic testing, including bronchoscopy, CT scan, and cultures for unusual pathogens.
Relapse may occur if therapy is discontinued before the resolution of chest x-ray findings, even if the patient is asymptomatic.
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