Lung Ultrasound Findings in COVID-19
The most common lung ultrasound (LUS) findings in screened studies and their relative prevalence were irregular pleural lines (27.9 to 89% in patients), pleural thickening (6.5 to 86%), separate “distinct or scattered” B-lines (16.6 to 88%), confluent “coalescent” B-lines with or without “white lung” (12 to 78.6%), pulmonary consolidations (31.1 to 77%), sub-pleural consolidations (8.06 to 73%) and pleural effusions (3.8% to 56%)[74–82] [Table 2] . Variability in prevalence of LUS findings is likely related to heterogeneity in the severity of the disease, as well as the timing of LUS in the course of the disease. For example, Mafort et al studied symptomatic healthcare professionals who had a positive RT‐PCR test for COVID‐19. They detected coalescent B‐lines and subpleural consolidations in 36% and 8.06% of patients, respectively. Bilateral involvement was seen in only 50.1% of patients. Of note, they studied patients during their first assessment and those hospitalized or undergoing intensive care were not included[76].
With regards to the distribution of LUS, bilateral distribution was noted in 50.1 to 100% of cases. A greater tendency to involve the posterior and lateral regions with less involvement of the anterior region was demonstrated by Smargiassi A et al [83]. Using a specific scoring system ranging from 0 to 3 (worst score, 3), they were able to demonstrate a higher prevalence of score 3 in posterior and lateral regions, and a higher prevalence of score 0 in the anterior regions in a population of non-critically ill patients. A more prominent involvement of the posterior and lower regions was also noted by Castelao J et al in 95.5% and 73.8% of studied patients, respectively[84]. Similar predilection for posterior and lower region involvement was described by Lu W et al, who also noted a subpleural and peripheral pulmonary zones distribution of LUS findings[78]. Interestingly, a more prominent involvement of the anterior areas of the lungs was noted in patients with severe disease relative to those with mild disease (36% vs 21% of patients, p .021)[85], and clinical deterioration was associated with loss of aeriation in anterior lung segments[86].