The temporal heterogeneity of usual interstitial pneumonia on chest CT.

The temporal heterogeneity that is a part of the pathologic UIP diagnosis can also be observed on chest CT. Earliest CT features of UIP include sub-pleural, basilar predominant opacities, and traction bronchiectasis. Late UIP presents radiographically with honeycombing that tends to increase in its peripheral extent and thickness over time. Temporal heterogeneity is manifest on CT with isolated areas of traction bronchiectasis representing early disease and separate areas of honeycombing representing more advanced disease in the same patient. Furthermore, some patients evolve from a probable UIP pattern to a UIP pattern. Therefore, a probable UIP pattern with its traction bronchiectasis and absence of honeycombing is an early UIP pattern. The most important questions become "Will it progress" and "Why should it not progress"?