A line: linear opacities extending from the periphery to the hila; they are caused by distention of anastomotic channels between peripheral and central lymphatics
B line: short horizontal lines situated perpendicularly to the pleural surface at the lung base; they represent edema of the interlobular septa
C line: reticular opacities at the lung base, representing Kerley's B lines en face.
Reference:
1. Kerley's A, B, and C Lines, IMAGES IN CLINICAL MEDICINE, NEJM, 2009, https://www.nejm.org/doi/full/10.1056/NEJMicm0708489
