Case 1-airspace disease:  fluffy, ill-defined, air-bronchograms, often in one lobe, need to know lobar and fissure anatomy to localize

Case 2-interstitial disease: linear, reticular, well-defined, Kerley B lines, often diffuse in distribution

Case 3-bronchial disease: tubular or rounded with radio-lucent centers, peribronchial cuffing, tram-tracking

Case 4-vascular disease:  radiodensities within vessel lumen, abnormal contour or size of vessels

Case 5-volume change:  empty spaces with increased volume (emphysema), shift of structures toward an area of abnormal opacity (collapse)