Pulm Edema - initially interstitial, later alveolar

INTERSTITIAL EDEMA (pt tachypneic, but no signs O/E)

interstitial tissues form a diffuse fine network throughout the lungs, converging over towards the hilum.

leakage of fluid from pulm vasc cause interstitial engorgement, seen radiographically as -

1.Obscuration of pulmonary vessels -  one of the earliest signs of interstitial pulmonary edema. (due to overlap with summating criss-cross interstitial shadows)

2.Thickening of interlobular septas.
seen mainly at lung bases near CP angles (bcos at these places they are oriented parallel to the xray beam in frontal projections), as short horizontal lines extending to the pleural surfce.(kerley B lines)


3.Thickening of short fissure (on right side)

4.Peribronchial cuffing  (thickening of bronchial and peribronchial tissues) - 

best appreciated in anterior segmental bronchus of upper lobe, which  is projected end on in frontal film, hence seen as a sharply defined ring shadow above and lateral to hilum, with an adjacent pulm artery branch.

Here, bronchial wall becomes thicker, denser and indistinct.

ALVEOLAR EDEMA (typical crepitations appear)

appearance similar to consolidation.
however, not as dense and homogenous as pneumonia
                 not confined to segments
                 quite unstable, tending to appear/disappear and change location rapidly.(evanescent)

characteristically seen as hazy poorly defined opacification of central portions of lung, radiating out from hila in a butterfly pattern.

HEART IN PULMONARY EDEMA

Most cases with pulm edema show cardiomegaly (CCF most common cause)

Cardiogenic pulm edema without cardiomegaly - acute MI

Non cardiogenic pulm edema - overinfusion of fluids, azotemia, shock, high altitudes.