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INTERSTITIAL LUNG DISEASE

Parenchymal lung disease or pulmonary fibrosis is a bilateral process which localises to the upper or lower lobes. It also presents as B lines on lung US (1). Volpicelli et al showed that the accuracy of lung US diagnosis of interstitial lung disease increases if more than two rib spaces show pathology bilaterally. The B lines in interstitial lung disease are not homogenous. Therefore even with multiple B lines, you may still see areas of normal lung with A lines interspersed between B lines in the same rib space. 

Interstitial lung disease can also be differentiated from CCF by looking closely at the pleura. In CCF the pleura is thin and regular. In interstitial lung disease, the pleura is usually thickened and irregular and contains hypoechoic areas (sub pleural consolidations). 

thickened pleura and B lines interspersed with normal lung

COVID-19

Covid-19 causes an interstitial lung disease beginning at the posterior bases bilaterally (2). Thus with Covid, it is essential to examine the posterior lung fields of L and R 5-6 (3,4).

In early disease, the CXR may be normal, making lung US a valuable tool at the bedside (5). Lung US for Covid-19 has has a high sensitivity and negative predictive value for Covid making it a good rule out test during a pandemic when the prevalence of Covid id high (6).  Increased severity of disease is associated with consolidation, anterior disease and small pleural effusions (usually just quad sign) (7,8). Lung US closely matches the CT findings (8). Thus, lung US features may be used to determine the presence of Covid, the severity of disease at presentation, track progress during the patient's hospital stay and determine disease resolution without the need for radiation.

Despite disease resolution, patients may still show signs of interstitial lung disease: especially in the posterior lung fields. Persistent changes are more common in patients who have been hospitalised for Covid-19 (9). 

COVID Score 1

Irregular pleura and scattered B lines

Irregular pleura and scattered B lines with areas of normal lung

COVID Score 2

Thickened pleura and confluent B lines

COVID Score 3

Thickened pleura, B lines and subpleural consolidation

Several prospective studies have developed scoring systems for Covid-19 lung US (10,11,12). These ultrasound all 12 zones of the lung L and R 1-6. 

Score 0: Normal pleura, no B lines

Score 1: Separated B lines

Score 2: Confluent B lines

Score 3: Consolidation

From Dell'Aquila P, et al Ultrasound J. 2022 Jun 1;14(1):21 (10)

A lung US score <7 has a high sensitivity for ruling out severe Covid-19, suggesting these patients may do well with outpatient management. A lung US score 8-20 is associated with disease of moderate severity and these patients should be admitted for management of symptoms and clinical deterioration. A score > 20 is associated with severe pneumonia: these patients will more likely need HDU/ICU. In a systematic review and validating study, Gill et al (1) showeed that a cut off score of 15 significantly predicted adverse outcomes and 28 day mortality.3

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REFERENCES

1. Volpicelli G, Mussa A, Garofalo G, et al. Bedside lung ultrasound in the assessment of alveolar-interstitial syndrome. Am J Emerg Med. 2006;24(6):689-696

2. Xu X, Yu C, Qu J et al Imaging and clinical features of patients with 2019 novel coronavirus SARS-CoV-2. Eur J Nucl Med Mol Imaging. 2020;47(5):1275-1280

3. Soldati G, Smargiassi A, Inchingolo R, et al. Proposal for International Standardization of the Use of Lung Ultrasound for Patients With COVID-19: A Simple, Quantitative, Reproducible Method. J Ultrasound Med.

4. Mento F, Perrone T, Macioce VN, et al. On the impact of different lung ultrasound imaging protocols in the evaluation of patients affected by coronavirus disease 2019. J Ultrasound Med2020; 40:2235–2238.

5. Colman J, Zamfir G, Sheehan F, Berrill M, Saikia S, Saltissi F. Chest radiograph characteristics in COVID-19 infection and their association with survival. Eur J Radiol Open. 2021

6. Di Gioia CC, Artusi N, Xotta G, Bonsano M, Sisto UG, Tecchiolli M, Orso D, Cominotto F, Amore G, Meduri S, Copetti R. Lung ultrasound in ruling out COVID-19 pneumonia in the ED: a multicentre prospective sensitivity study. Emerg Med J. 2022 Mar;39(3):199-205.

7. Gil-Rodríguez J, Martos-Ruiz M, Benavente-Fernández A, Aranda-Laserna P, Montero-Alonso MÁ, Peregrina-Rivas JA, Fernández-Reyes D, Martínez de Victoria-Carazo J, Guirao-Arrabal E, Hernández-Quero J. Lung ultrasound score severity cut-off points in COVID-19 pneumonia. A systematic review and validating cohort. Med Clin (Barc). 2023 Mar 10

8. Li K, Wu J, Wu F et al The Clinical and Chest CT Features Associated with Severe and Critical COVID-19 Pneumonia. Invest Radiol. 2020; 55(6): 1-6.

9. Demi L, Mento F, Di Sabatino A, Fiengo A, Sabatini U, Macioce VN, Robol M, Tursi F, Sofia C, Di Cienzo C, Smargiassi A, Inchingolo R, Perrone T. Lung Ultrasound in COVID-19 and Post-COVID-19 Patients, an Evidence-Based Approach. J Ultrasound Med. 2022 Sep;41(9):2203-2215.

10. Dell'Aquila P, Raimondo P, Racanelli V, De Luca P, De Matteis S, Pistone A, Melodia R, Crudele L, Lomazzo D, Solimando AG, Moschetta A, Vacca A, Grasso S, Procacci V, Orso D, Vetrugno L. Integrated lung ultrasound score for early clinical decision-making in patients with COVID-19: results and implications. Ultrasound J. 2022 Jun 1;14(1):21

11. Zhu ST, Tao FY, Xu JH, Liao SS, Shen CL, Liang ZH, Shi BB, Li Q. Utility of Point-of-Care Lung Ultrasound for Clinical Classification of COVID-19. Ultrasound Med Biol. 2021 Feb;47(2):214-221.

12. Ji L, Cao C, Gao Y, Zhang W, Xie Y, Duan Y, Kong S, You M, Ma R, Jiang L, Liu J, Sun Z, Zhang Z, Wang J, Yang Y, Lv Q, Zhang L, Li Y, Zhang J, Xie M. Prognostic value of bedside lung ultrasound score in patients with COVID-19. Crit Care. 2020 Dec 22;24(1)

13. Gil-Rodríguez J, Martos-Ruiz M, Benavente-Fernández A, Aranda-Laserna P, Montero-Alonso MÁ, Peregrina-Rivas JA, Fernández-Reyes D, Martínez de Victoria-Carazo J, Guirao-Arrabal E, Hernández-Quero J. Lung ultrasound score severity cut-off points in COVID-19 pneumonia. A systematic review and validating cohort. Med Clin (Barc). 2023 Mar 10