Idiopathic interstitial pneumonias: HRCT chest approach

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The approach to HRCT chest in patients with suspected idiopathic interstitial pneumonia (IIP) is with the aim to:

  • make sure an appropriate study requested i.e. HRCT chest with optimal individually adjusted protocol and ensure adequacy of the HRCT chest quality (see imaging protocol below)
  • meticulous scrutiny to detect all subtle findings, pattern, and distribution recognition as well as use of standard terminology in description of imaging findings
  • perhaps the most important role of radiologists is to differentiate the usual interstitial pneumonia (UIP) pattern of chronic fibrosing IIP from other subtypes and determine their level of confidence in the diagnosis as well as detecting features which help excluding IIP or suggesting other entities to be more likely
    • lung cysts
    • perilymphatic or centrilobular nodules
    • mosaic attenuation or air trapping
    • pleural thickening, plaques, calcification, or effusion 
    • dilated esophagus
    • sparing of the lung bases
  • radiologists should always make a comparison with older study or studies; it cannot be emphasized enough the importance of reviewing all prior studies and not only the most recent one cause sometimes interval changes between two consecutive studies are too subtle to be conspicuous but comparison with the older images can be revealing
  • besides, sometimes vital pieces of clinical information such as exposure history (smoking, drugs, organic protein exposure, dust etc.), age, and gender are not provided by the physicians which could completely change the list of differentials or even final diagnosis radiologists come up with; hence, radiologists need to actively try to obtain as much relevant information as possible. This can be done by developing good rapport with referring physicians and quick search in hospital information system (HIS).

In 2013 ATS/ERS revision IIPs are assigned into following major groups. Each entity has its own imaging characteristics, disease behavior, treatment and prognosis: