What causes Reverse pulmonary edema in lungs on chest radiography?
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Answer:
Peripheral and nondependent pulmonary opacities seen after relief of obstruction, such as in re-expansion pulmonary edema following rapid re-expansion of a chronically collapsed lung; contrasts with central bat-wing distribution of cardiogenic pulmonary edema; associated with clinical conditions including pneumothorax resolution, pleural effusion drainage, or rapid lung re-expansion after collapse for 3 or more days.
Why is it called so?
Named “Reverse pulmonary edema” due to its peripheral, nondependent distribution of opacities, which is the opposite (or photographic negative) of the typical central, perihilar, dependent bat-wing pattern observed in cardiogenic hydrostatic pulmonary edema.
Pathophysiology
Following relief of obstruction in a chronically collapsed lung, rapid re-expansion generates high negative intrapleural pressure, reperfusion injury, and endothelial permeability changes, leading to fluid leakage into peripheral, nondependent alveolar spaces and interstitium; hydrostatic factors may contribute secondarily, resulting in unilateral or bilateral nondependent opacities sparing central regions. Involvement of the pleura, pulmonary vasculature and lymphatic drainage can influence the radiographic pattern seen on chest radiography.
Alternative names: Re-expansion pulmonary edema, photographic negative of pulmonary edema
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