In recent years, great advances have been made in the use of lung ultrasound to detect pulmonary edema and interstitial changes in the lung. However, it is clear that B-lines oversimplify the description of the physical phenomena associated with their presence. The artifactual images that ultrasounds provide in interstitial pulmonary pathology are merely the ultimate outcome of the complex interaction of a specific acoustic wave with a specific three-dimensional biological structure. This interaction lacks a solid physical interpretation of the acoustic signs to support it. The aim of this paper was to describe the differences between the sonographic interstitial syndrome related to lung diseases and that related to cardiogenic edema in the light of current knowledge regarding the pleural plane’s response to ultrasound waves.