Organizing pneumonia: what is it? A conceptual approach and pictorial review.

Organizing pneumonia (formerly named bronchiolitis obliterans with organizing pneumonia or BOOP) is a clinical, radiological and histological entity that is classified as an Interstitial Lung Disease. The understanding of this family of diseases has seen great progress over the past twenty years. CT presentation of organizing pneumonia is polymorphous but a few patterns have been recently recognized as being more specific to this diagnosis. The aim of this work is to summarize new understandings of the clinical and histological presentation of the disease and to review the most relevant CT features.