12-25% of patients with community-acquired pneumonia have slowly resolving or non-resolving pneumonia.
Factors associated include systemic illnesses such as diabetes mellitus, congestive heart failure, renal insufficiency, age greater than 50 years, involvement of multiple lobes, chronic alcohol abuse and impaired local bronchial drainage and cough.
Lung cancer has been reported in up to 11% of patients with slowly resolving or non-resolving pneumonia.
If identifiable risk factors for delayed resolution are not present and continued improvement is not evident after 4 to 6 weeks, further diagnostic testing with a chest CT, fiberoptic bronchoscopy, and other studies should be considered.