Ultrasound signs of pulmonary fibrosis in systemic sclerosis as timely indicators for chest computed tomography

Abstract

Objectives: Systemic sclerosis (SSc) patients in the early stages of pulmonary fibrosis (PF) often have few or no symptoms, normal to borderline pulmonary function tests, and negative chest X-ray (CXR); high-resolution computed tomography (HRCT) is the only reliable means of detecting the early signs of PF. However, thoracic ultrasound (TUS) enables detection of pleural thickening, pleural/subpleural nodules, and other subpleural lung abnormalities across 70% of the subpleural surface. We reassessed concordance between TUS abnormalities and HRCT findings in SSc patients, to see whether TUS pleural line thickness (normally < 3.0 mm) could be used to earmark those with asymptomatic PF for timely HRCT assessment.

Method: In total, 175 SSc patients (nine males, 166 females), aged 46.46 ± 15.33 years, were given CXR, TUS, HRCT, echocardiography, and pulmonary function tests.

Results: In the 26 patients without HRCT signs of PF, pleural line thickness was ≤ 3.0 mm. In diffuse SSc, 97/137 patients showed pleural line thickening (between 3.0 and 5 mm) and subpleural nodules in 32/97; and 35/137 showed major pleural line thickening (≥ 5.0 mm) with nodules, with good concordance with HRCT patterns indicating lung fibrosis severity. HRCT was normal in 5/137, with pleural line thickness ≤ 3.0 mm.

Conclusions: TUS imaging of pleural/subpleural structures can detect ultrasonographic signs of initial PF prior to the onset of respiratory symptoms and function test abnormalities and, together with current criteria, could thereby enable exclusion of PF in SSc patients. Indicating some patients for selective referral to HRCT can thereby delay unwarranted procedures, provided that pulmonary function and TUS images are stable.