Introduction
Overview- Radiography allows assessment of lung size, position and density.
- The lateral projection is often used as a sole projection for thoracic radiography but this in fact provides poor detail of the dependent lung.
- If lateral projections are used, eg in the identification of pulmonary metastases, both laterals should be taken.
- Orthogonal views should be taken to locate the 3-dimensional position of a lesion.
- Ventrodorsal projections allow better visualization of the lung fields (especially accessory lobe) than the DV.
- The lung fields provide an inherent contrast within the thorax - a high KVp mAs should be used to maximize the range of densities available of pulmonary radiographs.
Use as short an exposure time as possible to minimize movement blur. - A grid is necessary if the depth of tissue is >10 cm.
- Exposure is normally made at the point of maximal inspiration.
- Expiratory films are occasionally useful to document small pneumothoraces, air trapping and bronchial and tracheal collapse.
- Care should be taken to include the entire pulmonary field.
- Examination is normally performed under sedation but heavily sedated animals may have poor inspiratory volumes making it impossible to obtain a view of a truely inflated lung.
- The VD projection should be avoided if there is a large volume of pleural fluid.
Most dyspneic animals will lie quietly in sternal recumbency for a DV projection with minimal restraint and no sedation.
Stressful handling of dyspneic animals may result in fatal decompensation.
- Dyspnea.
- Chronic cough.
- Screening for metastasis in the presence of malignant neoplasms elsewhere.
- Hemoptysis.
- Pre-anesthetic check.
- As part of minimum database in the investigation of many medical conditions.
- Ultrasonography is often more valuable than radiography in the presence of pleural fluid.
Dyspnea in the face of normal thoracic radiographs should prompt consideration of upper airway obstruction
, paraquat poisoning , pulmonary thromboembolism and acute viral pneumonia .
Not all serious lung pathology will result in radiographic abnormalities.
Sources
Publications
Refereed papers
- Nykamp S G, Scrivani P V & Dykes N L (2002) Radiographic signs of pulmonary disease: an alternative approach. Comp Contin Educ Pract Vet 24 (1), 25-34.
- Lamb C R & Neiger R (2000) Radiology corner - differential diagnosis of pulmonary cavitary lesions. Vet Rad Ultra 41 (4), 340-341.
