Nonresolving pneumonia is a common and frequently misunderstood problem faced by the practicing pulmonologist. While radiographic resolution of most infections is relatively long and lags behind clinical signs of recovery, data suggest that a variety of host defense problems are a consequence of systemic illness and are often involved. When such factors are not implicated, other specific etiologies should be sought, including unusual organisms like mycobacteria, higher order bacteria, and fungi. Noninfectious causes for delayed resolution include neoplastic disease, immunologic disease, thromboemboli, and inhalation injuries. This article discusses the natural history of common pneumonias to establish the usual clinical limits of resolution and outlines a diagnostic strategy to use when these limits are exceeded.
