This approach to HRCT chest in patients with suspected idiopathic interstitial pneumonia (IIP) is with the aim to:
make sure an appropriate study is requested, i.e. HRCT chest with optimal individually adjusted protocol and ensure adequacy of the HRCT chest quality (see imaging protocol below)
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meticulous scrutiny to detect all subtle findings, patterns, and distribution recognition, as well as the use of standard terminology in the description of imaging findings
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fibrotic changes
pulmonary volume loss
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distribution of disease
central
peribronchiovascular
peripheral - subpleural
patchy
diffuse
apicobasal gradient
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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 detect features which help exclude IIP or suggest 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 because 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.
chronic fibrosing IIPs: IPF and idiopathic non-specific interstitial pneumonia
smoking-related IIPs: respiratory bronchiolitis-associated interstitial lung disease and desquamative interstitial pneumonia
acute and subacute IIPs: acute interstitial pneumonia and cryptogenic organizing pneumonia
rare IIPs: idiopathic pleuroparenchymal fibroelastosis (added in 2013 revision) and lymphoid interstitial pneumonia
unclassifiable IIPs