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Review
. 2024 Feb;6(1):e230135.
doi: 10.1148/ryct.230135.

Thin-Section CT in the Categorization and Management of Pulmonary Fibrosis including Recently Defined Progressive Pulmonary Fibrosis

Rosita M Shah  1 , Ana M Kolansky  1 , Seth Kligerman  1
Affiliations
Review

Thin-Section CT in the Categorization and Management of Pulmonary Fibrosis including Recently Defined Progressive Pulmonary Fibrosis

Rosita M Shah et al. Radiol Cardiothorac Imaging. 2024 Feb.

Abstract

While idiopathic pulmonary fibrosis (IPF) is the most common type of fibrotic lung disease, there are numerous other causes of pulmonary fibrosis that are often characterized by lung injury and inflammation. Although often gradually progressive and responsive to immune modulation, some cases may progress rapidly with reduced survival rates (similar to IPF) and with imaging features that overlap with IPF, including usual interstitial pneumonia (UIP)-pattern disease characterized by peripheral and basilar predominant reticulation, honeycombing, and traction bronchiectasis or bronchiolectasis. Recently, the term progressive pulmonary fibrosis has been used to describe non-IPF lung disease that over the course of a year demonstrates clinical, physiologic, and/or radiologic progression and may be treated with antifibrotic therapy. As such, appropriate categorization of the patient with fibrosis has implications for therapy and prognosis and may be facilitated by considering the following categories: (a) radiologic UIP pattern and IPF diagnosis, (b) radiologic UIP pattern and non-IPF diagnosis, and (c) radiologic non-UIP pattern and non-IPF diagnosis. By noting increasing fibrosis, the radiologist contributes to the selection of patients in which therapy with antifibrotics can improve survival. As the radiologist may be first to identify developing fibrosis and overall progression, this article reviews imaging features of pulmonary fibrosis and their significance in non-IPF-pattern fibrosis, progressive pulmonary fibrosis, and implications for therapy. Keywords: Idiopathic Pulmonary Fibrosis, Progressive Pulmonary Fibrosis, Thin-Section CT, Usual Interstitial Pneumonia © RSNA, 2024.

Keywords: Idiopathic Pulmonary Fibrosis; Progressive Pulmonary Fibrosis; Thin-Section CT; Usual Interstitial Pneumonia.

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Conflict of interest statement

Disclosures of conflicts of interest: R.M.S. No relevant relationships. A.M.K. No relevant relationships. S.K. Deputy editor for Radiology: Cardiothoracic Imaging.

Figures

Diagram shows decision tree for pulmonary fibrosis with pattern and therapy considerations.
Figure 1:
Diagram shows decision tree for pulmonary fibrosis with pattern and therapy considerations.
Radiologic indeterminate for usual interstitial pneumonia–pattern fibrosis and unclassifiable fibrosis diagnosis in a 55-year-old male patient with a 30-pack-year smoking history and negative serologic findings and exposure history. (A) Axial thin-section CT image through the upper lobes shows subpleural cystic spaces in the right and left upper lobes (arrows) that are linearly arranged and multiple layers deep, demonstrating overlap with the imaging features of honeycombing (HC). (B) Axial thin-section CT image through the mid lungs shows mild ground-glass opacity and peripheral reticulation (open circles) without additional features of a specific diagnosis. (C) Photomicrograph from surgical right lung biopsy demonstrates interstitial pneumonia with lymphoid aggregates (long arrow) and pleuritis (short arrow), supporting an inflammatory cause of fibrosis including connective tissue disease–related interstitial lung disease (hematoxylin-eosin stain; low-power magnification). Airspace enlargement (open circle) was present without remodeling or HC and explains the presence of the above noted cystic spaces that can mimic HC at thin-section CT.
Figure 2:
Radiologic indeterminate for usual interstitial pneumonia–pattern fibrosis and unclassifiable fibrosis diagnosis in a 55-year-old male patient with a 30-pack-year smoking history and negative serologic findings and exposure history. (A) Axial thin-section CT image through the upper lobes shows subpleural cystic spaces in the right and left upper lobes (arrows) that are linearly arranged and multiple layers deep, demonstrating overlap with the imaging features of honeycombing (HC). (B) Axial thin-section CT image through the mid lungs shows mild ground-glass opacity and peripheral reticulation (open circles) without additional features of a specific diagnosis. (C) Photomicrograph from surgical right lung biopsy demonstrates interstitial pneumonia with lymphoid aggregates (long arrow) and pleuritis (short arrow), supporting an inflammatory cause of fibrosis including connective tissue disease–related interstitial lung disease (hematoxylin-eosin stain; low-power magnification). Airspace enlargement (open circle) was present without remodeling or HC and explains the presence of the above noted cystic spaces that can mimic HC at thin-section CT.
Radiologic probable usual interstitial pneumonia–pattern fibrosis and idiopathic pulmonary fibrosis diagnosis in a 68-year-old male patient with confirmation of histologic usual interstitial pneumonia in lung explant. (A, B) Axial thin-section CT images through the mid and lower lung zones show peripheral reticulation with mild ground-glass opacity (open circle in A), traction bronchiectasis (closed arrows in A), and traction bronchiolectasis (open arrow in A) without honeycombing. (C) Photomicrograph of the lung explant demonstrates microscopic honeycombing. Cystic airspaces containing mucus (open circles) are separated by fibrotic septae (arrows) (hematoxylin-eosin stain; magnification ×2.5). (D) Photomicrograph through one of many fibroblastic foci (arrow) present in the explant (hematoxylin-eosin stain; magnification ×10). (Image courtesy of Christopher Sande, MD.)
Figure 3:
Radiologic probable usual interstitial pneumonia–pattern fibrosis and idiopathic pulmonary fibrosis diagnosis in a 68-year-old male patient with confirmation of histologic usual interstitial pneumonia in lung explant. (A, B) Axial thin-section CT images through the mid and lower lung zones show peripheral reticulation with mild ground-glass opacity (open circle in A), traction bronchiectasis (closed arrows in A), and traction bronchiolectasis (open arrow in A) without honeycombing. (C) Photomicrograph of the lung explant demonstrates microscopic honeycombing. Cystic airspaces containing mucus (open circles) are separated by fibrotic septae (arrows) (hematoxylin-eosin stain; magnification ×2.5). (D) Photomicrograph through one of many fibroblastic foci (arrow) present in the explant (hematoxylin-eosin stain; magnification ×10). (Image courtesy of Christopher Sande, MD.)
Radiologic nonusual interstitial pneumonia pattern–fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 50-year-old male patient with scleroderma-associated interstitial lung disease. Progressive pulmonary fibrosis established by clinical and physiologic parameters was accompanied by a change in the pattern of interstitial lung disease. (A, B) Axial thin-section (A) and sagittal (B) CT images through the lower lobes show diffuse ground-glass opacity and mild reticulation with subpleural sparing (open circle in A). Esophageal dilatation (arrow in A) is present. Imaging features are consistent with nonspecific interstitial pneumonia which was confirmed at surgical biopsy. Note suture line in the lingula (open arrow in B). (C, D) Axial thin-section (C) and sagittal (D) CT images at the same levels obtained 2 years later show a change in the radiologic pattern of fibrosis which is now consistent with usual interstitial pneumonia. There is diffuse honeycombing and traction bronchiectasis. The patient underwent lung transplantation 4 months later. Pathologic evaluation of the explant confirmed usual interstitial pneumonia.
Figure 4:
Radiologic nonusual interstitial pneumonia pattern–fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 50-year-old male patient with scleroderma-associated interstitial lung disease. Progressive pulmonary fibrosis established by clinical and physiologic parameters was accompanied by a change in the pattern of interstitial lung disease. (A, B) Axial thin-section (A) and sagittal (B) CT images through the lower lobes show diffuse ground-glass opacity and mild reticulation with subpleural sparing (open circle in A). Esophageal dilatation (arrow in A) is present. Imaging features are consistent with nonspecific interstitial pneumonia which was confirmed at surgical biopsy. Note suture line in the lingula (open arrow in B). (C, D) Axial thin-section (C) and sagittal (D) CT images at the same levels obtained 2 years later show a change in the radiologic pattern of fibrosis which is now consistent with usual interstitial pneumonia. There is diffuse honeycombing and traction bronchiectasis. The patient underwent lung transplantation 4 months later. Pathologic evaluation of the explant confirmed usual interstitial pneumonia.
Radiologic usual interstitial pneumonia pattern–fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 58-year-old female patient with rheumatoid arthritis–associated interstitial lung disease. Progressive pulmonary fibrosis established by clinical and physiologic parameters was accompanied by worsening fibrosis at imaging. (A) Sagittal CT image through the right lower lobe shows subpleural predominant coarse reticulation with honeycombing (open arrows), traction bronchiectasis (arrow), and intermixed areas of ground-glass opacity. More mild findings are observed in the right middle lobe and anterior segment of the right upper lobe. (B) Sagittal CT image 2.5 years later shows decreased ground-glass opacity and increasing extent of honeycombing (open circle) and size of the cysts (open arrows).
Figure 5:
Texture-based CT quantification demonstrates progressive disease in a 68-year-old male patient with hypersensitivity pneumonitis. (A) Coronal CT image with texture analysis overlay reveals a data-driven texture analysis score of 26%. (B) Coronal CT image with texture analysis overlay at 3-year follow-up demonstrates progression, with a data-driven texture analysis score of 39%. (Image courtesy of David Lynch, MD, and Stephen M. Humphries, PhD, Quantitative Imaging Laboratory, National Jewish Health.)
Radiologic usual interstitial pneumonia pattern–fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 58-year-old female patient with rheumatoid arthritis–associated interstitial lung disease. Progressive pulmonary fibrosis established by clinical and physiologic parameters was accompanied by worsening fibrosis at imaging. (A) Sagittal CT image through the right lower lobe shows subpleural predominant coarse reticulation with honeycombing (open arrows), traction bronchiectasis (arrow), and intermixed areas of ground-glass opacity. More mild findings are observed in the right middle lobe and anterior segment of the right upper lobe. (B) Sagittal CT image 2.5 years later shows decreased ground-glass opacity and increasing extent of honeycombing (open circle) and size of the cysts (open arrows).
Figure 6:
Radiologic usual interstitial pneumonia pattern–fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 58-year-old female patient with rheumatoid arthritis–associated interstitial lung disease. Progressive pulmonary fibrosis established by clinical and physiologic parameters was accompanied by worsening fibrosis at imaging. (A) Sagittal CT image through the right lower lobe shows subpleural predominant coarse reticulation with honeycombing (open arrows), traction bronchiectasis (arrow), and intermixed areas of ground-glass opacity. More mild findings are observed in the right middle lobe and anterior segment of the right upper lobe. (B) Sagittal CT image 2.5 years later shows decreased ground-glass opacity and increasing extent of honeycombing (open circle) and size of the cysts (open arrows).
Radiologic usual interstitial pneumonia–pattern fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 45-year-old female patient with systemic sclerosis and rheumatoid arthritis. The distribution of honeycombing (HC) supports connective tissue disease–related interstitial lung disease. (A) Axial thin-section CT image at the level of the main pulmonary artery (*) shows HC in the anterolateral upper lobes and superior segment of the left lower lobe. (B) Axial thin-section CT image at the level of the diaphragm shows exuberant HC. The esophagus is dilated and fluid filled (arrow). (C) Coronal CT reconstruction shows exuberant HC with sharp demarcation from normal lung parenchyma (arrow). At lung transplantation, the explant revealed histologic usual interstitial pneumonia with architectural distortion due to diffuse HC with fibroblastic foci.
Figure 7:
Radiologic usual interstitial pneumonia–pattern fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 45-year-old female patient with systemic sclerosis and rheumatoid arthritis. The distribution of honeycombing (HC) supports connective tissue disease–related interstitial lung disease. (A) Axial thin-section CT image at the level of the main pulmonary artery (*) shows HC in the anterolateral upper lobes and superior segment of the left lower lobe. (B) Axial thin-section CT image at the level of the diaphragm shows exuberant HC. The esophagus is dilated and fluid filled (arrow). (C) Coronal CT reconstruction shows exuberant HC with sharp demarcation from normal lung parenchyma (arrow). At lung transplantation, the explant revealed histologic usual interstitial pneumonia with architectural distortion due to diffuse HC with fibroblastic foci.
Radiologic nonusual interstitial pneumonia pattern–fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 63-year-old male patient with hypersensitivity pneumonitis and a history of dust exposure. Lung biopsy demonstrated noncaseating granulomas in a perilymphatic and peribronchial distribution. (A–C) Axial thin-section CT images obtained in inspiration demonstrate widespread ground-glass opacity, mosaic lung attenuation pattern (open circles in B and C), and upper zonal peribronchial reticulation and traction bronchiectasis (arrows in B). (D–F) Axial thin-section CT images obtained in expiration accentuate geographic hyperlucent zones supporting lobular air trapping (open circles in E and F).
Figure 8:
Radiologic nonusual interstitial pneumonia pattern–fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 63-year-old male patient with hypersensitivity pneumonitis and a history of dust exposure. Lung biopsy demonstrated noncaseating granulomas in a perilymphatic and peribronchial distribution. (A–C) Axial thin-section CT images obtained in inspiration demonstrate widespread ground-glass opacity, mosaic lung attenuation pattern (open circles in B and C), and upper zonal peribronchial reticulation and traction bronchiectasis (arrows in B). (D–F) Axial thin-section CT images obtained in expiration accentuate geographic hyperlucent zones supporting lobular air trapping (open circles in E and F).
Evolving radiologic usual interstitial pneumonia–pattern fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 64-year-old male patient with shortened telomeres and fibrotic hypersensitivity pneumonitis. Progressive pulmonary fibrosis was supported by rapidly progressive fibrosis at 9-month CT follow-up. (A) Baseline CT image at presentation. Axial thin-section CT image at the level of the aortic arch demonstrates coarse reticular opacities, confluent subpleural areas of fibrosis, traction bronchiectasis, and a few mildly hypoattenuated lobules (arrows). (B) Axial thin-section CT image at the level of the diaphragm shows mild ground-glass opacity, traction bronchiectasis, and areas of subpleural cystic change suggestive of honeycombing. (C, D) Axial thin-section CT images obtained 9 months later demonstrate worsening fibrosis in both the upper (C) and lower (D) lobes with increasing coarse reticulation, traction bronchiectasis, and honeycombing. Confluent bands of subpleural fibrosis in the upper and lower lobes have also increased. This case highlights the importance of thin-section CT characteristics in recognizing an underlying fibrogenic lung disease when there is radiologic usual interstitial pneumonia–pattern fibrosis.
Figure 9:
Evolving radiologic usual interstitial pneumonia–pattern fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 64-year-old male patient with shortened telomeres and fibrotic hypersensitivity pneumonitis. Progressive pulmonary fibrosis was supported by rapidly progressive fibrosis at 9-month CT follow-up. (A) Baseline CT image at presentation. Axial thin-section CT image at the level of the aortic arch demonstrates coarse reticular opacities, confluent subpleural areas of fibrosis, traction bronchiectasis, and a few mildly hypoattenuated lobules (arrows). (B) Axial thin-section CT image at the level of the diaphragm shows mild ground-glass opacity, traction bronchiectasis, and areas of subpleural cystic change suggestive of honeycombing. (C, D) Axial thin-section CT images obtained 9 months later demonstrate worsening fibrosis in both the upper (C) and lower (D) lobes with increasing coarse reticulation, traction bronchiectasis, and honeycombing. Confluent bands of subpleural fibrosis in the upper and lower lobes have also increased. This case highlights the importance of thin-section CT characteristics in recognizing an underlying fibrogenic lung disease when there is radiologic usual interstitial pneumonia–pattern fibrosis.
Radiologic nonusual interstitial pneumonia–pattern fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 60-year-old male patient with Hermansky-Pudlak syndrome. (A, B) Axial thin-section CT images through the upper (A) and mid (B) lung zones show axially distributed ground-glass opacity with reticulation, subpleural cysts, and honeycombing. Histologic evaluation of the explant revealed fibrosing nonspecific interstitial pneumonia. Vacuolated pneumocytes characteristic of Hermansky-Pudlak syndrome were present.
Figure 10:
Radiologic nonusual interstitial pneumonia–pattern fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 60-year-old male patient with Hermansky-Pudlak syndrome. (A, B) Axial thin-section CT images through the upper (A) and mid (B) lung zones show axially distributed ground-glass opacity with reticulation, subpleural cysts, and honeycombing. Histologic evaluation of the explant revealed fibrosing nonspecific interstitial pneumonia. Vacuolated pneumocytes characteristic of Hermansky-Pudlak syndrome were present.
Radiologic nonusual interstitial pneumonia–pattern fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 49-year-old female patient with chronic granulomatous inflammation due to sarcoidosis. (A) Initial axial CT image demonstrates extensive micronodules with perilymphatic distribution. (B) Axial thin-section CT image obtained 15 years later shows central and upper zonal predominant fibrosis with volume loss, architectural distortion, coarse linear opacities, and absence of previously observed micronodules. A reduction in the degree of nodularity in association with developing fibrosis supports evolving granulomatous inflammation. In this case, slowly progressive fibrosis due to sarcoidosis was treated by immune modulation.
Figure 11:
Radiologic nonusual interstitial pneumonia–pattern fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 49-year-old female patient with chronic granulomatous inflammation due to sarcoidosis. (A) Initial axial CT image demonstrates extensive micronodules with perilymphatic distribution. (B) Axial thin-section CT image obtained 15 years later shows central and upper zonal predominant fibrosis with volume loss, architectural distortion, coarse linear opacities, and absence of previously observed micronodules. A reduction in the degree of nodularity in association with developing fibrosis supports evolving granulomatous inflammation. In this case, slowly progressive fibrosis due to sarcoidosis was treated by immune modulation.
Radiologic nonusual interstitial pneumonia–pattern fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 55-year-old female patient with pleuroparenchymal fibroelastosis (PPFE) associated with a telomerase mutation. Progressive pulmonary fibrosis was established by rapidly progressive fibrosis at 12-month CT follow-up. (A) Coronal CT image through the level of the carina shows upper lobe–predominant confluent areas of subpleural fibrosis with associated pleural thickening and traction bronchiectasis (arrows). (B) Coronal CT image 12 months later shows progression of PPFE with increasing size and extent of confluent areas of fibrosis with increasing pleural retraction and volume loss. Histologic evaluation of the explant confirmed PPFE.
Figure 12:
Radiologic nonusual interstitial pneumonia–pattern fibrosis and nonidiopathic pulmonary fibrosis diagnosis in a 55-year-old female patient with pleuroparenchymal fibroelastosis (PPFE) associated with a telomerase mutation. Progressive pulmonary fibrosis was established by rapidly progressive fibrosis at 12-month CT follow-up. (A) Coronal CT image through the level of the carina shows upper lobe–predominant confluent areas of subpleural fibrosis with associated pleural thickening and traction bronchiectasis (arrows). (B) Coronal CT image 12 months later shows progression of PPFE with increasing size and extent of confluent areas of fibrosis with increasing pleural retraction and volume loss. Histologic evaluation of the explant confirmed PPFE.
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