High-resolution CT in smoking-related interstitial lung diseases.

In addition to chronic obstructive pulmonary disease (COPD) and bronchogenic carcinoma, smoking can also cause interstitial lung diseases (ILDs) such as respiratory bronchiolitis (RB), RB with ILD (RB-ILD), desquamative interstitial pneumonia (DIP), Langerhans cell granulomatosis (LCG) and idiopathic pulmonary fibrosis-usual interstitial pneumonia (IPF-UIP). However, smoking seems to have a protective effect against hypersensitivity pneumonitis (HP), sarcoidosis and organising pneumonia (OP). High-resolution computed tomography (HRCT) has a pivotal role in the differential diagnosis. RB is extremely frequent in smokers, and is considered a marker for smoking exposure. It has no clinical relevance in itself since most patients with RB are asymptomatic. It is frequent to observe the association of RB with other smoking-related diseases, such as LCG or pulmonary neoplasms. In RB-ILD, HRCT features are more conspicuous and diffuse than in RB, but there is no definite cut-off between the two entities and any distinction can only be made by integrating imaging and clinical data. RB, RB-ILD and DIP may represent different degrees of the same pathological process, consisting in a bronchiolar and alveolar inflammatory reaction to smoking. Smoking is also a well-known risk factor for pulmonary fibrosis. Multidisciplinary discussion and follow-up can generally solve even the most difficult cases.

Radiological diagnosis of fibrosing interstitial lung diseases: innovations and controversies.

Following the introduction of new effective antifibrotic drugs, interest in fibrosing interstitial lung diseases (FILD) has been renewed. In this context, radiological evaluation of FILD plays a cardinal role. Radiological diagnosis is possible in about 50% of the cases, which allows the initiation of effective therapy, thereby avoiding invasive procedures such as surgical lung biopsy. Usual interstitial pneumonia (UIP) pattern may be diagnosed based on clinical, radiological, and pathological data. High-resolution computed tomography features of UIP have been widely described in literature; however, interpreting them remains challenging, even with specific expertise on the subject. Diagnostic difficulties are understandable given the continuous evolution of FILD classifications and their complexity. Both early-stage diseases and advanced or combined patterns are not easily classifiable, and many end up being labelled 'indeterminate´ or 'unclassifiable´. Especially in these cases, optimal patient management involves collaboration and communication between different specialists. Here, we discuss the most critical aspects of radiological interpretation in FILD diagnosis based on the most recent classifications. We believe that the clinicians´ awareness of radiological diagnostic issues of FILD would improve comprehension and dialogue between physicians and radiologists, leading to better clinical practice.