Normally, resistance is so low that flowcan be increased up to 3x normal withoutincrease in pressure
Pulmonary Interstitial EdemaX-ray Findings
Thickening of the interlobular septa
Kerley B lines
Peribronchial cuffing
Wall is normally hairline thin
Thickening of the fissures
Fluid in the subpleural space in continuity withinterlobular septa
Pleural effusions
Pulmonary Interstitial Edema
Kerley B Lines
B=distended interlobular septa
Location and appearance
Bases
1-2 cm long
Horizontal in direction
Perpendicular to pleural surface
Kerley B Lines are short, white lines perpendicularto the pleural surface at the lung base.
Kerley A and C Lines
A=connective tissue near bronchoarterialbundle distends
Location and appearance
Near hilum
Run obliquely
Longer than B lines
C=reticular network of lines
C Lines probably don’t exist
Kerley A and C Lines form a patternof interlacing lines in the lung
Peribronchial Cuffing
Interstitial fluid accumulates aroundbronchi
Causes thickening of bronchial wall
When seen on end, looks like little“doughnuts”
Peribronchial cuffing results when fluid-thickenedbronchial walls become visible producing”doughnut-like” densities in the lung parenchyma
Fluid in The Fissures
Fluid collects in the subpleural space
Between visceral pleura and lungparenchyma
Normal fissure is thickness of asharpened pencil line
Fluid may collect in any fissure
Major, minor, accessory fissures, azygousfissure
Fluid in the major or minor fissure (shown here)produces thickening of the fissure beyond the pencil-point thickness it can normally attain
Pleural Effusion
Laminar effusions collect beneathvisceral pleura
In loose connective tissue betweenlung and pleura
Same location for “pseudotumors”
Laminar pleural effusions can be difficult to see. Aerated lungshould normally extend to the inner margin of the ribs. The whiteband of fluid seen here (white arrow) is a laminar effusion,separating aerated lung from the inner rib margin.
Aerated lung stopshere
Inner margin of therib starts here
CephalizationA Proposed Mechanism
If hydrostatic pressure >10 mm Hg, fluidleaks in to interstitium of lung
Compresses lower lobe vessels first
Perhaps because of gravity
Resting upper lobe vessels “recruited”to carry more blood
Upper lobes vessels increase in sizerelative to lower lobe
Cephalization means pulmonary venous hypertension, so long as the person is erect when the chest x-ray is obtained.
Left Atrial PressuresCorrelated With Pathologic Findings
Fluid in the subpleural space incontinuity with interlobular septa
Pleural effusions
Congestive Heart FailurePulmonary alveolar edema
Acinar shadow
Outer third of lung frequently spared
Bat-wing or butterfly configuration
Lower lung zones more affected thanupper
In pulmonary alveolar edema, fluid presumably spills over from theinterstitium to the air spaces of the lung producing a fluffy, confluent“bat-wing” like pattern of disease.
Pulmonary Interstitial Edema
Pulmonary Alveolar Edema
Pulmonary Alveolar EdemaClearing
Generally clears in 3 days or less
Resolution usually begins peripherallyand moves centrally
Differential DiagnosisKerley B lines and Peribronchial cuffing
Cardiac 30%
Renal 30%
ARDS None
Differential DiagnosisDistribution of Pulmonary Edema