The emerging importance of interstitial lung abnormality on chest computed tomography: a narrative review

Purpose: This review summarizes the current definition, epidemiology, risk factors, and management strategies for interstitial lung abnormality (ILA).Current concepts: ILA is an incidental radiologic finding on chest computed tomography (CT) that suggests interstitial lung disease in individuals without a prior clinical diagnosis. As defined by the Fleischner Society and recently updated by the American Thoracic Society, ILA is characterized by features such as ground-glass opacities, reticulation, lung distortion, traction bronchiectasis, honeycombing, or non-emphysematous cysts involving ≥5% of any lung zone. In addition, ILA is classified into non-subpleural, subpleural non-fibrotic, and subpleural fibrotic subtypes to facilitate assessment of progression risk. The prevalence of ILA ranges from 3% to 10% in the general population. Risk factors for ILA progression include advanced age, cigarette smoking, other inhalational exposures, and genetic susceptibility, particularly the MUC5B promoter polymorphism. Clinically, ILA is associated with increased all-cause and respiratory mortality, accelerated decline in lung function, and a higher risk of lung cancer and pulmonary fibrosis.Discussion and conclusion: ILA may represent an early or subclinical stage of pulmonary fibrosis. Therefore, standardized reporting and risk-based clinical management are essential. Patients with high-risk features, particularly those with the subpleural fibrotic subtype, require active monitoring with pulmonary function tests and longitudinal CT surveillance to mitigate adverse outcomes and enable timely intervention.