Major imaging findings of simple nonloculated pleural effusions on upright X ray?
The most common imaging finding of a pleural effusion is blunting of the lateral costophrenic sulcus on upright frontal chest radiography or blunting of the posterior costophrenic sulcus on upright lateral chest radiography. A pleural effusion usually has a sharply marginated, concave–upward curved border between the lung and pleural space, which is known as the “meniscus” sign. Because the posterior costophrenic angle is more dependent than the lateral costophrenic angle, smaller pleural effusions are more apparent on the lateral view (with >75 mL of fluid) than on the frontal view (with >200 mL of fluid). Moderate to large pleural effusions usually obscure the ipsilateral hemidiaphragm ( Figure 21-2, A ). Less common manifestations of pleural effusions include apparent elevation and medial flattening of the hemidiaphragm with lateral displacement of the diaphragmatic apex and an increase in distance (>2 cm) between the inferior surface of the lung and the gastric bubble on the left. The lateral decubitus view is the most sensitive radiographic view for detection of a pleural effusion and can detect 5 mL of pleural fluid.