To provide an approach for diagnosing and categorising interstitial lung abnormalities (ILA) and highlight the differences between ILA and interstitial lung disease (ILD).

Insterstitial lung abnormality (ILA) is a relatively new term, defined as the presence of nondependent abnormalities affecting 5% or more of a lung zone seen on computed tomography (CT) in cases where interstitial lung disease (ILD) is not suspected [1,2]. ILA has a prevalence of up to 9% in smokers and 7% in non-smokers, and is associated with increasing age, inhalational exposures, and genetics [1]. ILA is clinically significant as it correlates with higher all-cause mortality and can progress to ILD [1]. Over 20% of...

ILA is subclassified based on the zones of the lung affected (upper, mid and/or lower), its distribution (peripheral or central) and whether fibrosis is present [1,2]. Examples of ILA in different locations are shown in Figures 1 and 2. [Fig 1] [Fig 2] Fibrosis is indicated by architectural distortion and traction bronchiectasis (shown in Figure 3), with or without honeycombing (shown in Figure 4) [1,2]. Fissural retraction is also a useful feature of fibrosis (shown in Figure 5). [Fig 3] [Fig 4] [Fig 5] Other...

It is important for radiologists to be familiar with ILA as it is a common finding particularly in the aging demographic and is associated with potential progression to ILD. At the same time, it is important to be aware of the distinction between radiological ILA and clinical ILD, to avoid the diagnostic pitfall of overcalling ILDs.

Hata A, Schiebler ML, Lynch DA, Hatabu H. Interstitial Lung Abnormalities: State of the Art. Radiology 2021;301:19-34. Hatabu H, Hunninghake GM, Richeldi L, Brown KK, Wells AU, Remy-Jardin M, Verschakelen J, Nicholson AG, Beasley MB, Christiani DC, San José Estépar R, Seo JB, Johkoh T, Sverzellati N, Ryerson CJ, Graham Barr R, Goo JM, Austin JHM, Powell CA, Lee KS, Inoue Y, Lynch DA. Interstitial lung abnormalities detected incidentally on CT: a Position Paper from the Fleischner Society. Lancet Respir Med 2020;8:726-37. Copley SJ, Wells...