Pleural Space Diseases

23 Pleural Space Diseases

5. What routine diagnostic test is needed to confirm the presence of pleural effusion?

Thoracic radiographs are usually necessary to confirm the presence of a pleural effusion. Radiographically, the effusion can be classified as free or encapsulated. Free fluid moves within the pleural cavity and is most characteristic of transudative effusions. Encapsulated fluid is trapped by adhesions and is often associated with chronic exudative effusions, such as pyothorax. The radiographic diagnosis of pleural effusion depends on finding one or more of the following radiographic signs: (1) the presence of interlobar fissure lines; (2) rounding of lung margins at the costophrenic angles; (3) separation of lung lobe borders away from the thoracic wall; (4) scalloping of the lung lobe margins dorsal to the sternum; (5) blurring of the cardiac silhouette; and (6) widening of the mediastinum. The radiographic views that are most helpful for recognizing small amounts (less than 100 ml) of pleural fluid are the lateral recumbent and ventrodorsal views. The earliest sign of pleural effusion is accumulation of fluid dorsal to the sternum in the lateral recumbent position, resulting in scalloping of the lung lobe borders as they retract from the thoracic walls. The ventrodorsal view is preferable to the dorsoventral view for dogs with small amounts of pleural fluid. Radiographs taken during expiration are also helpful when evaluating a dog with a small volume of pleural fluid because the volume of the lungs is less at this phase of breathing; therefore, the volume of effusion is relatively greater and is spread over a smaller area. Dramatic radiographic changes are associated with a large volume pleural effusion. Retraction and separation of the lung lobes from the thoracic wall should be present in all radiographic views. Thoracic width usually increases on the ventrodorsal and dorsoventral views. Lung lobes can collapse to half their original volumes. In the lateral and dorsoventral views, the heart, the mediastinum and the diaphragm may be totally obscured by fluid. Dorsal elevation of the trachea and caudal displacement of the liver and diaphragm are commonly present on the lateral view.

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Jul 31, 2016 | Posted by in INTERNAL MEDICINE | Comments Off on Pleural Space Diseases

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