The idiopathic interstitial pneumonias: understanding key radiological features

HRCT images demonstrating the typical features of UIP; reticulation (thin arrows), honeycombing (thick arrows), and traction bronchiectasis (arrowheads) in a basal, subpleural predominance. (a) In the early stages there may only be irregularity/reticulation seen at the pleura–parenchymal border, whilst (b) honeycombing is characteristic in end-stage disease. The lungs are generally of reduced volume.

Histologically proven NSIP. HRCT images demonstrating (a) GGO in a typical bilateral, symmetrical, predominantly subpleural, and lower zone predominance (arrowheads). GGO may be the only finding in one-third of cases. (b) Reticulation/irregular linear opacities (thin arrows) occur in 50–85%. Traction bronchiectasis occurs in 35–95% (thick arrows). (c) CT with lung windows showing GGO can be peribronchovascular in up to 50% (dotted arrows) and can be indistinguishable from organising pneumonia.

HRCT images demonstrating proven COP. Consolidation (short arrows) occurs in 90%. It is multifocal with a peribronchovascular (a) and subpleural (b)(dotted arrows) distribution in 50%. Within the consolidation dilated airways are often seen (arrowheads). Coarse linear opacities are often seen, predominantly within the lower zones (white arrows) (b).

CT with lung windows demonstrating biopsy-proven COP. (a) COP presenting as multiple masses. Note the air bronchograms within the masses. (b) HRCT demonstrating the reverse halo sign (arrows), which is areas of GGO surrounded by crescent and ring-shaped consolidation.

CT with lung windows demonstrating histologically proven AIP in a young women post-partum. There is lower zone predominance with consolidation and GGO with lobular sparing (arrow).

HRCT images demonstrating RBILD. There is subtle multifocal ground glass attenuation, some of which is centrilobular in distribution (arrows) within the upper zones on inspiration (a). There is accentuation of the mosaic pattern on expiration (b) confirming air-trapping.

HRCT image demonstrating histologically proven DIP. Image shows GGO, which is in a patchy and diffuse distribution (seen in 18% of cases), but in over 50% there is predominantly a peripheral distribution.

HRCT images displaying the typical features of histologically proven LIP. (a) GGO is invariable (occurs in a diffuse distribution two thirds) with centrilobular nodules (arrows), although as nodules occur in the distribution of the lymphatics they can also occur in subpleural and peribronchovascular locations. (b) Thin-walled perivascular cysts occur in two-thirds of cases (arrowheads). (c) Diffuse nodular GGO with atypical features of nodular consolidation (white arrowheads) and traction bronchiectasis (white arrows).