Interstitial lung abnormality (ILA) refers to incidental bilateral non-dependent CT patterns including reticulation, traction bronchiectasis and honeycombing that may be symptomatic, may progress to fibrosis and portend a higher all cause mortality risk 7.
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Epidemiology
Although may vary from population to population its general prevalence in a routine cohort of CT older adults (subjects older than 60 years of age) as 4–9% of smokers and 2–7% of non-smokers 6,10.
Terminology
Definition: incidental bilateral non-dependent ground-glass opacity, reticulation, distortion, traction bronchiectasis, honeycombing or non-emphysematous cystic change affecting more than 5% of any lung zone without a demonstrable cause.
50% may progress over 5 years, particularly subpleural and fibrotic changes.
Imaging subclassification
Publications (2020-2021) have suggested sub-classification into the following types 7,9
fibrotic
-
non fibrotic
non fibrotic subpleural
non fibrotic non subpleural
Practical points
The 5% cut-off is arbitrary and the significance of so-called ILA is still being worked out 11.
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