May Be Caused by

 Common

Absent pulmonary artery

Idiopathic pulmonary edema

Prolonged lateral decubitus position

Pulmonary arterial thromboembolism

Pulmonary artery hypoplasia

Pulmonary artery occlusion

Pulmonary emphysema

Pulmonary lobectomy

Rapid reexpansion of lung

Swyer-James syndrome

Unilateral aspiration

Unilateral lung contusion

 Uncommon

Bronchial obstruction

Bronchogenic carcinoma

Bronchogenic cyst

Carcinoid

Catheter malposition with infusion into pulmonary artery and lung

Congenital heart disease

Foreign body in bronchus

Mucus plug

Pulmonary vein obstruction

Systemic-pulmonary artery shunt

Unilateral ductus shunt

Unilateral veno-occlusive disease