ICU Chest Films > Fluid in the Chest > Pulmonary Edema > Alveolar Edema

Alveolar Edema

Alveolar edema occurs when the pulmonary venous pressure exceeds 30 mmHg. Therefore, the signs of interstitial edema are present in patients who have progressed to alveolar edema. Classically, alveolar edema appears as bilateral opacities that extend in a fan shape outward from the hilum in a "bat wing" pattern. As the edema worsens, the opacities become increasingly homogenous. These water-density opacities may contrast with air-filled bronchi which, in normally aerated parenchyma are invisible. The visible appearance of previously imperceptible bronchi is known as air-bronchograms.

Haziness of the pulmonary hila are due to vessel enlargment in a patient with CHF. Air bronchograms are visible in he right upper lobe.