The Senile Lung as a Possible Source of Pitfalls on Chest Ultrasonography and Computed Tomography

Background: Age-associated changes in the pulmonary system could be detected with imaging techniques. Widespread use of lung ultrasonography (US) requires characterization of a normal pattern. Objectives: To compare US and computed tomography (CT) findings in healthy subjects undergoing both techniques (with CT as the gold standard). Methods: We prospectively selected 59 subjects undergoing chest CT and US on the same day, without a history of smoking, respiratory symptoms, or known pulmonary pathologies. There were 44 patients in group 1 (age ≥60 years - elderly) and 15 patients in group 2 (age ≤50 years - young). Lung US was performed with a convex and a linear probe, and 10 chest areas per patient were analyzed. Convex and linear probe agreement was evaluated by means of the Cohen κ statistic; Fisher's exact test was used to compare categorical variables between groups. Results: Isolated B-lines were frequent in both group 1 (54.5%) and group 2 (40.0%); the number of chest areas positive for B-lines increased with age (16.1% in group 1 vs. 5.3% in group 2, p = 0.0028). In group 2, we found that 37.5% of subjects with B-lines had at least 1 chest area with multiple B-lines, but only 2 subjects had 2 or more. Moreover, in group 1 the chest CT documented a reticular pattern (2.3%), areas of increased density (9.1%), ground glass (6.8%), cysts (2.3%), bronchiectasis (22.7%), and bronchial thickening (6.8%); in group 2, only cysts (6.7%) and bronchiectasis (6.7%) were found. Conclusions: The senile lung is characterized by mild changes on CT and US. Chest areas positive for B-lines increase with age, and focal multiple B-lines can be found. However, diffuse patterns, especially in symptomatic subjects, suggest a different diagnosis.