Introduction

Overview

• Radiography has limited value in assessment of dynamic disease of upper airways, eg laryngeal paralysis and soft palate disorders unless fluoroscopy available.
• In most cases additional investigations, eg bronchoscopy and tracheal wash Transtracheal wash will be required for diagnosis.

Radiographic considerations
Larynx and trachea

• The lateral projection is generally the most informative as the trachea and larynx are obscured by the spine on the VD projection.
• The skyline projection of the thoracic inlet may be helpful in identifying tracheal collapse.
• For evaluating cervical trachea and larynx the ET tube should be removed when exposure made as this will hinder evaluation and may result in displacement of the trachea mimicking a cervical mass.

Upper airways

• The neck should be in a neutral position and head carefully padded to avoid rotation when evaluating the pharyngeal region.
• Rotation will result in the soft palate appearing thickened.

Bronchi

• Left lateral and DV projections allow best visualization of bronchi.
• The lung fields provide an inherent contrast within the thorax - a high KVp, low 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.

Restraint

• 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.
• General anesthesia is required to obtain a true lateral projection of head and neck. The endotracheal tube often hinders evaluation as it distorts soft palate and laryngeal position - if possible it should be removed for exposure.
• 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.

Indications

• Nasal discharge Nasal discharge.
• Stertor.
• Dyspnea.
• Signs of upper airway obstruction Brachycephalic airway obstruction syndrome.
• Post-trauma.
• Cough.

Radiographic anatomy

Interpretation

Additional studies

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Carlisle C H, Biery D N & Thrall D E (1991) Tracheal and laryngeal tumors in the dog and cat - literature review and 13 additional patients. Vet Radiol 32 (5), 229-235 VetMedResource.