Radiographic Distribution as a Diagnostic Clue in Pulmonary Disease

Because some disease processes produce radiographic abnormalities that occur in characteristic distributions in the chest, classifying the position and appearance of these suggestive features and the underlying diseases provides a tool by which diagnostic accuracy might be improved. The goal of this review is to offer to the chest clinician a taxonomy of these disease entities that can produce characteristic chest radiographic distributions. These radiographic distributions often reflect anatomic or physiologic conditions that drive the radiographic appearance; for example, foramen of Morgagni diaphragmatic hernias most commonly present in the right ventral chest, consistent with the anatomic location of the diaphragmatic foramen. This taxonomy includes 3 distributional categories: (1) upper versus lower lung zone-predominant processes, (2) central versus peripheral processes, and (3) processes with distinctive focal locations, eg, "photonegative appearance" as in chronic eosinophilic pneumonia. It is hoped that this taxonomy aids the chest clinician in generating and streamlining a differential diagnosis and in ascertaining the specific cause of diseases with radiographic abnormalities.