Differentiating Smoking-Related Interstitial Fibrosis (SRIF) from Usual Interstitial Pneumonia (UIP) with Emphysema Using CT Features Based on Pathologically Proven Cases

Advances in Concept and Imaging of Interstitial Lung Disease

Although idiopathic pulmonary fibrosis (IPF) is a type of idiopathic interstitial pneumonia (IIP), it is different from other IIPs. IPF also differs from interstitial lung disease (ILD) with known causes, including connective tissue disease, exposure, cysts and/or airspace filling disease, and sarcoidosis. More than 90% of IPFs demonstrate progressive disease. Non-IPF ILD has been classified as progressive pulmonary fibrosis on the basis of disease behavior (progressive disease that gets worse over time) as opposed to classification based on cause and/or morphologic characteristics. Progressive fibrosis predictors in ILD include demographic characteristics, underlying connective tissue disease, more extensive disease at CT, honeycombing and usual interstitial pneumonia (UIP) pattern at CT, and greater impairment of lung function. Hypersensitivity pneumonitis (HP), a type of ILD, is separated into fibrotic and nonfibrotic types. Extensive peribronchiolar metaplasia supports the diagnosis of fibrotic HP over UIP, as does predominantly peribronchiolar disease with relative subpleural sparing at CT. Interstitial lung abnormality (ILA) is incidentally identified at CT; thus, ILA is under radiologist purview. Subpleural fibrotic ILA is a prognostic imaging biomarker, predictive of worse prognosis. Photon-counting CT can provide high spatial resolutions of up to 125 μm (in-plane) and 200 μm (through-plane) for improved evaluation of abnormalities.

Quantitative Imaging Methods in Combined Pulmonary Fibrosis and Emphysema

TOPIC IMPORTANCE

Combined pulmonary fibrosis and emphysema (CPFE) is an underdiagnosed syndrome in which individuals have variable degrees of pulmonary fibrosis and emphysema. Patients with CPFE have high morbidity, including poor exercise tolerance and increased development of comorbidities. CPFE mortality also seems to outpace that of lone emphysema and pulmonary fibrosis. A major limitation to rigorous, large-scale studies of CPFE has been the lack of a precise definition for this syndrome. A 2022 American Thoracic Society/European Respiratory Society/Japanese Respiratory Society/Latin American Thoracic Association research statement called attention to fundamental gaps in our understanding of CPFE and highlighted the potential use of quantitative imaging techniques to better define CPFE.

REVIEW FINDINGS

Broadly, CPFE has been defined using visual interpretation of chest CT imaging documenting the presence of both emphysema and fibrosis, with varying distributions. When quantitative approaches were involved, varying thresholds of emphysema and fibrosis on imaging have been used across different studies.

SUMMARY

This review is structured into three primary themes, starting with early imaging studies, then evaluating the use of quantitative methods and imaging-based thresholds, both in large population studies and single-center cohorts to define CPFE and assess patient outcomes. It concludes by discussing current challenges and how to focus our efforts so that quantitative imaging methods can effectively address the most pressing clinical dilemmas in CPFE.

[Smoking-related interstitial lung disease : Radiological findings, histopathological correlations, and clinical observations]

CLINICAL/METHODOLOGICAL ISSUE

Identifying smoking-related interstitial lung diseases (SRILD) in smokers is challenging, as clinical manifestations can be nonspecific, and there is a variety of SRILD entities that not only interconnect but can also overlap.

RADIOLOGICAL STANDARD PROCEDURES

In diagnosing SRILD, imaging techniques such as high-resolution computed tomography (HRCT) allow the identification of characteristic features, serving as crucial pieces of the puzzle for definitive differentiation.

PERFORMANCE

Studies have demonstrated that HRCT exhibits a sensitivity of approximately 80-90% in identifying SRILD, with a specificity around 70-80%. The conclusive diagnosis often requires a correlation between histopathological findings and clinical observations.

PRACTICAL RECOMMENDATIONS

Regular monitoring of smokers, especially when experiencing symptoms like shortness of breath and cough, coupled with a comprehensive diagnosis of SRILD, is crucial for accurate identification and individualized therapy.

Smoking-Related Interstitial Lung Disease and Emphysema

Diagnosis and treatment of patients with smoking-related lung diseases often requires multidisciplinary contributions to optimize care. Imaging plays a key role in characterizing the underlying disease, quantifying its severity, identifying potential complications, and directing management. The primary goal of this article is to provide an overview of the imaging findings and distinguishing features of smoking-related lung diseases, specifically, emphysema/chronic obstructive pulmonary disease, respiratory bronchiolitis-interstitial lung disease, smoking-related interstitial fibrosis, desquamative interstitial pneumonitis, combined pulmonary fibrosis and emphysema, pulmonary Langerhans cell histiocytosis, and E-cigarette or vaping related lung injury.

Central Role of CT in Management of Pulmonary Fibrosis

With the approval of antifibrotic medications to treat patients with idiopathic pulmonary fibrosis and progressive pulmonary fibrosis, radiologists have an integral role in diagnosing these entities and guiding treatment decisions. CT features of early pulmonary fibrosis include irregular thickening of interlobular septa, pleura, and intralobular linear structures, with subsequent progression to reticular abnormality, traction bronchiectasis or bronchiolectasis, and honeycombing. CT patterns of fibrotic lung disease can often be reliably classified on the basis of the CT features and distribution of the condition. Accurate identification of usual interstitial pneumonia (UIP) or probable UIP patterns by radiologists can obviate the need for a tissue sample-based diagnosis. Other entities that can appear as a UIP pattern must be excluded in multidisciplinary discussion before a diagnosis of idiopathic pulmonary fibrosis is made. Although the imaging findings of nonspecific interstitial pneumonia and fibrotic hypersensitivity pneumonitis can overlap with those of a radiologic UIP pattern, these entities can often be distinguished by paying careful attention to the radiologic signs. Diagnostic challenges may include misdiagnosis of fibrotic lung disease due to pitfalls such as airspace enlargement with fibrosis, paraseptal emphysema, recurrent aspiration, and postinfectious fibrosis. The radiologist also plays an important role in identifying complications of pulmonary fibrosis-pulmonary hypertension, acute exacerbation, infection, and lung cancer in particular. In cases in which there is uncertainty regarding the clinical and radiologic diagnoses, surgical biopsy is recommended, and a multidisciplinary discussion among clinicians, radiologists, and pathologists can be used to address diagnosis and management strategies. This review is intended to help radiologists diagnose and manage pulmonary fibrosis more accurately, ultimately aiding in the clinical management of affected patients. ©RSNA, 2024 Supplemental material is available for this article.

Interstitial Lung Abnormality in Asian Population

Interstitial lung abnormalities (ILAs) are radiologic abnormalities found incidentally on chest computed tomography (CT) that can be show a wide range of diseases, from subclinical lung fibrosis to early pulmonary fibrosis including definitive usual interstitial pneumonia. To clear up confusion about ILA, the Fleischner society published a position paper on the definition, clinical symptoms, increased mortality, radiologic progression, and management of ILAs based on several Western cohorts and articles. Recently, studies on long-term outcome, risk factors, and quantification of ILA to address the confusion have been published in Asia. The incidence of ILA was 7% to 10% for Westerners, while the prevalence of ILA was about 4% for Asians. ILA is closely related to various respiratory symptoms or increased rate of treatment-related complication in lung cancer. There is little difference between Westerners and Asians regarding the clinical importance of ILA. Although the role of quantitative CT as a screening tool for ILA requires further validation and standardized imaging protocols, using a threshold of 5% in at least one zone demonstrated 67.6% sensitivity, 93.3% specificity, and 90.5% accuracy, and a 1.8% area threshold showed 100% sensitivity and 99% specificity in South Korea. Based on the position paper released by the Fleischner society, I would like to report how much ILA occurs in the Asian population, what the prognosis is, and review what management strategies should be pursued in the future.

Multidisciplinary Approach to the Diagnosis of Idiopathic Interstitial Pneumonias: Focus on the Pathologist's Key Role

Idiopathic Interstitial Pneumonias (IIPs) are a heterogeneous group of the broader category of Interstitial Lung Diseases (ILDs), pathologically characterized by the distortion of lung parenchyma by interstitial inflammation and/or fibrosis. The American Thoracic Society (ATS)/European Respiratory Society (ERS) international multidisciplinary consensus classification of the IIPs was published in 2002 and then updated in 2013, with the authors emphasizing the need for a multidisciplinary approach to the diagnosis of IIPs. The histological evaluation of IIPs is challenging, and different types of IIPs are classically associated with specific histopathological patterns. However, morphological overlaps can be observed, and the same histopathological features can be seen in totally different clinical settings. Therefore, the pathologist's aim is to recognize the pathologic-morphologic pattern of disease in this clinical setting, and only after multi-disciplinary evaluation, if there is concordance between clinical and radiological findings, a definitive diagnosis of specific IIP can be established, allowing the optimal clinical-therapeutic management of the patient.

Lung Imaging in COPD Part 1: Clinical Usefulness

COPD is a condition characterized by chronic airflow obstruction resulting from chronic bronchitis, emphysema, or both. The clinical picture is usually progressive with respiratory symptoms such as exertional dyspnea and chronic cough. For many years, spirometry was used to establish a diagnosis of COPD. Recent advancements in imaging techniques allow quantitative and qualitative analysis of the lung parenchyma as well as related airways and vascular and extrapulmonary manifestations of COPD. These imaging methods may allow prognostication of disease and shed light on the efficacy of pharmacologic and nonpharmacologic interventions. This is the first of a two-part series of articles on the usefulness of imaging methods in COPD, and it highlights useful information that clinicians can obtain from these imaging studies to make more accurate diagnosis and therapeutic decisions.

Combined Pulmonary Fibrosis and Emphysema: Comparative Evidence on a Complex Condition

Combined pulmonary fibrosis and emphysema (CPFE) is a clinical syndrome characterized by upper lobe emphysema and lower lobe fibrosis manifested by exercise hypoxemia, normal lung volumes, and severe reduction of diffusion capacity of carbon monoxide. It has varying prevalence worldwide with a male predominance, and with smoking history of more than 40 pack-years being a common risk factor. The unique imaging features of CPFE emphasize its distinct entity, aiding in the timely detection of pulmonary hypertension and lung cancer, both of which are common complications. High-resolution computed tomography (HRCT) is an important diagnostic and prognostic tool, while lung cancer is an independent factor that alters the prognosis in CPFE patients. Treatment options for CPFE are limited, but smoking cessation, usual treatments of pulmonary fibrosis and emphysema, and avoidance of environmental exposures are encouraged.

Smoking-related interstitial lung disease

Exposure to smoke is associated with the development of diseases of the airways and lung parenchyma. Apart from chronic obstructive pulmonary disease (COPD), in some individuals, tobacco smoke can also trigger mechanisms of interstitial damage that result in various pathological changes and pulmonary fibrosis. A causal relation has been established between tobacco smoke and a group of entities that includes respiratory bronchiolitis-associated interstitial lung disease (RB-ILD), desquamative interstitial pneumonia (DIP), Langerhans cell histiocytosis (LCH), and acute eosinophilic pneumonia (AEP). Smoking is considered a risk factor for idiopathic pulmonary fibrosis (IPF); however, the role and impact of smoking in the development of this differentiated clinical entity, which has also been called combined pulmonary fibrosis and emphysema (CPFE) as well as nonspecific interstitial pneumonia (NIP), remains to be determined. The definition of smoking-related interstitial fibrosis (SRIF) is relatively recent, with differentiated histological characteristics. The likely interconnection between the mechanisms involved in inflammation and pulmonary fibrosis in all these processes often results in an overlapping of clinical, radiological, and histological features in the same patient that can sometimes lead to radiological patterns of interstitial lung disease that are impossible to classify. For this reason, a combined approach to diagnosis is recommendable. This combined approach should be based on the joint interpretation of the histological and radiological findings while taking the clinical context into consideration. This paper aims to describe the high-resolution computed tomography (HRCT) findings in this group of disease entities in correlation with the clinical manifestations and histological changes underlying the radiological pattern.

Chronic Obstructive Pulmonary Disease and Small Airways Diseases

The small airways are a common target of injury within the lungs and may be affected by a wide variety of inhaled, systemic, and other disorders. Imaging is critical in the detection and diagnosis of small airways disease since significant injury may occur prior to pulmonary function tests showing abnormalities. The goal of this article is to describe the typical imaging findings and patterns of small airways diseases. An approach which divides the imaging appearances into four categories (tree-in-bud opacities, poorly defined centrilobular nodules, mosaic attenuation, and emphysema) will provide a framework in which to formulate appropriate and focused differential diagnoses.

Raucherassoziierte interstitielle Lungenerkrankungen

Klinisches Problem

Raucherassoziierte interstitielle Lungenerkrankungen umfassen heterogene pulmonale Pathologien, deren korrekte Diagnostik prognostische und therapeutische Konsequenzen hat. In diesem Artikel werden die gängigsten raucherassoziierten interstitiellen Lungenerkrankungen beschrieben sowie eine strukturierte Herangehensweise präsentiert, welche den diagnostischen Arbeitsprozess erleichtern kann.

Empfehlungen für die Praxis

Die Computertomographie (CT) besitzt einen hohen Stellenwert in der Diagnose der raucherassoziierten interstitiellen Lungenerkrankungen und kann dazu beitragen, Lungenbiopsien zu verhindern. Um eine hohe diagnostische Genauigkeit zu erreichen, sollten standardisierte Untersuchungsprotokolle sowie eine strukturierte Herangehensweise in der Befundung zur Anwendung kommen. In den entzündlich dominierten Stadien der respiratorischen Bronchiolitis (RB), der respiratorischen Bronchiolitis mit interstitieller Lungenerkrankung (RB-ILD) sowie der desquamativen interstitiellen Pneumonie (DIP) haben die Beendigung des Rauchens sowie Steroide den größten therapeutischen Effekt. Bei fibrotischen Veränderungen (z. B. im Rahmen einer idiopathischen pulmonalen Fibrose [IPF]) können antifibrotische Therapien mit Pirfenidon und Nintedanib zum Einsatz kommen. Patienten mit dem Verdacht auf raucherassoziierte interstitielle Lungenerkrankung sollten in multidisziplinären Boards abgeklärt und behandelt werden.

Syndrome of Combined Pulmonary Fibrosis and Emphysema: An Official ATS/ERS/JRS/ALAT Research Statement

Background: The presence of emphysema is relatively common in patients with fibrotic interstitial lung disease. This has been designated combined pulmonary fibrosis and emphysema (CPFE). The lack of consensus over definitions and diagnostic criteria has limited CPFE research. Goals: The objectives of this task force were to review the terminology, definition, characteristics, pathophysiology, and research priorities of CPFE and to explore whether CPFE is a syndrome. Methods: This research statement was developed by a committee including 19 pulmonologists, 5 radiologists, 3 pathologists, 2 methodologists, and 2 patient representatives. The final document was supported by a focused systematic review that identified and summarized all recent publications related to CPFE. Results: This task force identified that patients with CPFE are predominantly male, with a history of smoking, severe dyspnea, relatively preserved airflow rates and lung volumes on spirometry, severely impaired DlCO, exertional hypoxemia, frequent pulmonary hypertension, and a dismal prognosis. The committee proposes to identify CPFE as a syndrome, given the clustering of pulmonary fibrosis and emphysema, shared pathogenetic pathways, unique considerations related to disease progression, increased risk of complications (pulmonary hypertension, lung cancer, and/or mortality), and implications for clinical trial design. There are varying features of interstitial lung disease and emphysema in CPFE. The committee offers a research definition and classification criteria and proposes that studies on CPFE include a comprehensive description of radiologic and, when available, pathological patterns, including some recently described patterns such as smoking-related interstitial fibrosis. Conclusions: This statement delineates the syndrome of CPFE and highlights research priorities.

Diagnosis and Management of Fibrotic Interstitial Lung Diseases

Nonidiopathic pulmonary fibrosis (non-IPF) progressive fibrotic interstitial lung diseases (PF-ILDs) are a heterogeneous group of ILDs, often challenging to diagnose, although an accurate diagnosis has significant implications for both treatment and prognosis. A subgroup of these patients experiences progressive deterioration in lung function, physical performance, and quality of life after conventional therapy. Risk factors for ILD progression include older age, lower baseline pulmonary function, and a usual interstitial pneumonia pattern. Management of non-IPF P-ILD is both pharmacologic and nonpharmacologic. Antifibrotic drugs, originally approved for IPF, have been considered in patients with other fibrotic ILD subtypes, with favorable results in clinical trials.

Interstitial Lung Abnormalities: What Radiologists Should Know

Interstitial lung abnormalities (ILAs) are radiologic abnormalities found incidentally on chest CT that are potentially related to interstitial lung diseases. Several articles have reported that ILAs are associated with increased mortality, and they can show radiologic progression. With the increased recognition of ILAs on CT, the role of radiologists in reporting them is critical. This review aims to discuss the clinical significance and radiologic characteristics of ILAs to facilitate and enhance their management.

Immunopathogenesis and therapeutic potential of macrophage influx in diffuse parenchymal lung diseases

INTRODUCTION

The diffuse parenchymal lung diseases (DPLD)/interstitial lung diseases (ILD) are progressive lung disorders with usually unclear etiology, poor long-term survival and no effective treatment. Their pathogenesis is characterized by alveolar epithelial cell injury, inflammation, epithelial-mesenchymal transition, and parenchymal fibrosis. Macrophages play diverse roles in their development, both in the acute phase and in tissue repair.

AREAS COVERED

In this review, we summarize the current state of knowledge regarding the role of macrophages and their phenotypes in the immunopathogenesis of DPLDs; CVD-ILD, UIP, NSIP, DIP, RB-ILD, AIP, HP, Sarcoidosis, etc. Our goal is to update the understanding of the immune mechanisms underlying the initiation and progression of fibrosis in DPLDs. This will help in identification of biomarkers and in developing novel therapeutic strategies for DPLDs. A thorough literature search of the published studies in PubMed (from 1975 to 2020) was done.

EXPERT OPINION

The macrophage associated inflammatory markers needs to be explored for their potential as biomarkers of disease activity and progression. Pharmacological targeting of macrophage activation may reduce the risk of macrophage activation syndrome (MAS) and help improving the survival and prognosis of these patients.

Idiopathic pulmonary fibrosis: Significance of the usual interstitial pneumonia (UIP) CT-scan patterns defined in new international guidelines

INTRODUCTION

The new 2018 international guidelines for diagnosing usual interstitial pneumonia (UIP)/idiopathic pulmonary fibrosis (IPF) by CT scan split the old pattern possible UIP (2011 IPF guidelines) into two new patterns: probable UIP and indeterminate for UIP. However, the proportions and prognoses of these new CT-scan patterns are not clear.

METHODS

We used a monocentric retrospective cohort of 322 patients suspected of having IPF (University Hospital of Rennes; Competence Center for Rare Lung Diseases; 1 January 2012-31 December 2017). All patients initially diagnosed by CT scan as possible UIP were included. The chest CT-scans were then reclassified according to the new 2018 international guidelines by 3 observers. These data were then subjected to survival analysis with multivariate Cox regression using a composite endpoint of death, lung transplantation, a decline of≥10% in forced vital capacity (FVC), or hospitalization.

RESULTS

Of the 89 possible UIP patients included, 74 (83%) were reclassified as probable UIP and 15 (17%) as indeterminate for UIP. Probable UIP patients were more likely to meet the composite endpoint (56/74 [75.7%] vs. 5/15 [33%] patients; HR [IC 95%] =3.12 [1.24; 7.83], P=0.015). Multivariate analysis indicated that the probable UIP pattern was associated with significantly increased risk of reaching the composite endpoint (HR [95% CI]=2.85[1.00; 8.10], P=0.049).

CONCLUSION

The majority of possible UIP diagnoses corresponded to probable UIP, which was associated with a significantly worse prognosis than indeterminate for UIP. This distinction between these two CT patterns emphasizes the relevance of the new international guidelines for the diagnosis of IPF.

A 54-Year-Old Man Presenting With Progressive Dyspnea and Interstitial Lung Abnormalities

CASE PRESENTATION

A 54-year-old man presented with a 6-month history of progressive dyspnea occurring at rest and with minimal exertion. His medical history was notable for hypertension, non-insulin-dependent diabetes, coronary artery disease, and factor V Leiden heterozygosity. His social history was notable for a 43-pack-year smoking history but was otherwise unremarkable.

Combined pulmonary fibrosis and emphysema as a clinicoradiologic entity: Characterization of presenting lung fibrosis and implications for survival

BACKGROUND

The prevalence of classifiable and unclassifiable causes of lung fibrosis and its implications for survival are mostly unknown in combined pulmonary fibrosis and emphysema (CPFE).

MATERIALS AND METHODS

Patients with >10% involvement of both emphysema and lung fibrosis seen over 11 years at our institution were reviewed independently by expert radiologists for fibrotic and emphysematous findings and overall fibrotic CT pattern. Underlying interstitial lung disease (ILD) diagnoses and baseline demographic and clinical characteristics were collated and assessed for predictors of comparative survival.

RESULTS

In this retrospective cohort, 179 CPFE patients were identified and categorized as 58 usual interstitial pneumonia/idiopathic pulmonary fibrosis (UIP/IPF) (32%), 42 secondary ILD (23%), and 79 unclassifiable ILD (44%). The most prevalent (47%) radiologic pattern was 'unclassifiable', followed by 'consistent' and 'possible' UIP pattern in 38%. Adjusted predictors of mortality for the cohort as a whole included age (HR 1.03[1.01-1.06], P = 0.002), percent predicted diffusing capacity for carbon monoxide (unit HR 0.97 [0.96-0.99], P = 0.001), honeycombing (HR 1.58 [1.02-2.43], P = 0.04), and right ventricular dysfunction (HR 2.28 [1.39-3.97], P = 0.002). Survival was similar between CPFE with secondary ILD and CPFE with UIP/IPF, while CPFE with unclassifiable ILD had better comparative survival (Log rank = 0.026).

CONCLUSIONS

Our findings suggest only about a third of CPFE patients represent suspected UIP/IPF; the majority were clinically and radiologically unclassifiable ILD whose survival was comparatively better. Identifiable or secondary causes of lung fibrosis in CPFE occurred in about a fifth of presenting patients.

Smoking-Related Lung Disease

Smoke from cigarettes and other sources may induce a variety of patterns of lung injury. While smoking related lung diseases, in general, have a better prognosis than many other diffuse lung diseases, they may be a cause of significant symptoms and, in some cases, may even require lung transplantation. On histology, the manifestations of these patterns range from reversible inflammation to irreversible emphysema or fibrosis. High-resolution chest CT plays a critical role in the diagnosis of smoking related lung diseases. It has several roles including (1) helping determine diagnosis, (2) assessing the pattern of injury that is present, (3) evaluating the extent and severity of disease, and (4) determining the response to treatment. The practicing radiologist must have a knowledge of the clinical, pathologic, and imaging features of the differnent patterns of lung injury associated with smoke inhalation.