Annotated image - Kerley lines
How can you confirm that these findings are indeed due to an acute process rather than chronic interstitial disease?
Look at a previous chest x-ray, or repeat the film after diuresis.
Kerley A lines (orange arrows), Kerley B lines (blue arrows) and Kerley C lines (green arrows) are all seen, and all represent essentially the same thing; expansion of the interstitial space by fluid.