In addition to being misdiagnosed as lung disease, recumbent atelectasis is important because the increased radiographic opacity of the collapsed lung causes border effacement, or silhouetting, of any soft tissue lesion in the dependent lung, rendering it inconspicuous in the radiograph.1 This phenomenon results commonly in lesions in the dependent lung not being visible radiographically in the lateral view (Fig. 25-2). The most significant aspect of this phenomenon is in the situation where the lesion is small and is not visible in the VD or DV view, such as commonly occurs with a lung nodule or small mass. If only one lateral view is made of such patients, and the lesion happens to be in the dependent lung and also in a region where it is not visible in the VD or DV radiograph, the lesion will be missed (Fig. 25-3). The collapse of the dependent lung is the main reason why both the left lateral and right lateral views should be included in every routine thoracic radiographic examination. If only one lateral view is obtained, a significant number of patients will be diagnosed incorrectly.2 Assessing the absolute and relative size of pulmonary vessels is an important process of thoracic radiographic interpretation.3 The pulmonary artery and vein in the right cranial lobe are used commonly as a basis for assessing the pulmonary circulation. It is important to be able to identify these two vessels specifically and to be able to compare the size of the right cranial lobe pulmonary artery to the size of the right cranial lobe pulmonary vein without having other vessels superimposed. The pulmonary vessels in the right cranial lung lobe are more conspicuous in a left lateral than in a right lateral radiograph (Fig. 25-5). This is caused mainly by the dorsal displacement of the right cranial lobe that occurs when the patient is in right lateral recumbency resulting in the right cranial lobar vessels being superimposed on the left cranial lobar vessels.
Principles of Radiographic Interpretation of the Thorax
Positioning: Dog and Cat
Lateral Views
Atelectasis
Cranial Lobe Vessels
Principles of Radiographic Interpretation of the Thorax
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