The Role of Transthoracic Ultrasound in the Study of Interstitial Lung Disease: HRCT Versus Ultrasound Pattern

Background: High-resolution computed tomography (HRCT) is the gold standard in the diagnosis and follow-up of interstitial lung diseases (ILDs), however it is associated with high radiation exposure. Aim of the study: Since Transthoracic Ultrasound (TUS) is a safe radiation-free diagnostic procedure, the aim of this study was to establish a complementary role for this imaging method in the approach of ILDs. Methods: TUS examination was performed in 43 consecutive patients (32 males and 11 females, aged 70.77±8.32 years) with pulmonary fibrosis (28 UIP/IPF, 4 CPFE, 2 NSIP, 4 HP and 5 ILD waiting for diagnostic definition). Ultrasound findings were compared with the corresponding HRTC scans and the ultrasound thickness of the hyperechoic pleural was correlated with functional parameters, whose impairment indicates the severity of the lung disease. Results: All patients showed a thickening of the hyperechoic pleural line with no difference between dominant HRTC patterns (ground glass, honeycombing, mixed pattern) (p=NS) and between IPF patients with a different stage of disease assessed by the GAP index (p=NS). However we found a correlation between the thickness of the hyperechoic pleural line and the impairment in functional parameters (FVC%, DLCO%, meters traveled and Nadir value of SaO2% during 6mWT). Conclusion: TUS may be an useful complementary tool in the assessment of an early peripheral interstitium involvement in ILDs, essentially represented by the findings of a thickened and irregular hyperechoic pleural line and of subpleural nodules/cysts, although HRCT remains the gold standard in the definition of ILD pattern, disease’s extent and follow-up.