CT features of pathologically proven smoking-related interstitial fibrosis: compared with emphysema and usual interstitial pneumonia

Objectives: To differentiate smoking-related interstitial fibrosis (SRIF) from emphysema and usual interstitial pneumonia (UIP) using CT. Materials and methods: From January 2016 to October 2023, a total of 123 patients who underwent lung surgery with pathologically proven SRIF (n = 23), emphysema (n = 50), and UIP (n = 50) were included. Three radiologists retrospectively reviewed preoperative chest CTs for imaging features of centrilobular/paraseptal emphysema, multiple thin-walled cysts (MTWC), honeycombing, traction bronchiectasis, subpleural ground-glass opacity (GGO)/reticulation, and presence of smoking-related disease (SRD) and compared the CT features by subgroup. Results: A total of 123 patients (23 SRIF, 50 emphysema, 50 UIP; mean age, 64.9 ± 8.96 years; 99 males) were involved. Centrilobular emphysema, paraseptal emphysema, MTWC, honeycombing, traction bronchiectasis, subpleural GGO/reticulation, and SRD were identified in SRIF (100%, 100%, 73.9%, 8.7%, 100%, 100%, 47.8%), emphysema (94%, 60%, 2%, 2%, 4%, 8%, 10%), and UIP (48%, 40%, 0%, 42%, 100%, 100%, 6%) cases, respectively. In the univariable analysis of SRIF and emphysema, MTWC, traction bronchiectasis, subpleural GGO/reticulation, and the presence of SRD were predictive features of SRIF (all p < 0.05). In the multivariable analysis of SRIF and emphysema, MTWC and subpleural GGO/reticulation were predictive of SRIF (all p < 0.05). In both univariable and multivariable analyses of SRIF and UIP, MTWC and the presence of SRD were predictive features of SRIF (all p < 0.05), whereas honeycombing was significant only in univariable analysis (p = 0.01). Conclusion: Imaging features of MTWC, subpleural GGO/reticulation, and the presence of SRD on CT may help differentiate SRIF from emphysema and UIP. Key Points: Question SRIF is recognized as a separate entity; however, insufficient radiological studies have been conducted. Findings CT imaging features of MTWC, subpleural GGO/reticulation, and the presence of SRD are predictive factors for SRIF. Clinical relevance SRIF, emphysema, and UIP have overlapping imaging/clinical features but different treatments and prognoses. As treatment for UIP slows the disease progression, accurate differentiation based on imaging findings is essential for improving prognosis.