Equine throat and thorax

Question 1

Clinical significance

Answer 1

• Equine radiography is an important test in the evaluation of the equine airway and thorax
• Radiography of these regions is an important tool to evaluate morphologic abnormalities
• Endoscopic evaluation required for functional abnormality detection
• These 2 modalities are complimentary

Question 2

Radiographic anatomy (structures to know)

Answer 2

1. Epiglottis
2. Aryepiglottic fold
3. Corniculate process of the arytenoid
4. Lateral ventricals
5. Larynx
6. Trachea
7. Soft palate
8. Guttural pouch (medial and lateral compartments)
9. Stylohyoid bone

Question 3

Radiographic lesions: larynx

Answer 3

• Epiglottic entrapment
  
  • Aryepiglottic fold envelops epiglottis
  • May or not be detectable
  • Tip of epiglottis appears blunt, bulbous and malformed

Question 4

Radiographic lesions: pharynx

Answer 4

• Dorsal displacement of soft palate
  
  • Caudal free margin of soft palate moves dorsal to epiglottis, creating a functional obstruction
    
    • Inflammation in guttural pouch causes vagal palsy, leading to soft palate flaccidity
    • Retropharyngeal lylmph nodes are in direct contact with pharyngeal branch of the vagus nerve, and may result in compression and irritation
    • Congenital hypoplasia of epiglottis
• Lesions that result in reduced pharyngeal volume:
  
  • Retropharyngeal abscess
  • Retropharyngeal lymphadenopathy

Question 5

Radiographic signs: pharyngeal disease

Answer 5

• Decreased gas content
• Alteration in size and color
• Changes in size, shape, position of soft palate

Question 6

Radiographic signs: guttural pouch disease

Answer 6

• Increased air content (tympany)
• Increased soft tissue/fluid opacity
• Intraluminal mass

Question 7

Radiographic lesions: guttural pouch

Answer 7

• Tympany
  
  • Severe gaseous distention of the guttural pouch (seen in young)
  • Often unilateral
  • Due to inflammation or malformation of auditory tube–one way valve created
  • Compresses the pharynx and displaces the larynx and trachea ventrally
• Guttural pouch effusions
  
  • Fluid/gas interface seen because of horizontal beam radiography
    
    • Hemorrhage (mycosis) or exudates (empyema)

Question 8

T/F: In equine lung disease, lesion detail in adult patients is optimized by placing the lesion closer to the cassette (i.e. lesion in left lung obtain a right-left lateral)

Answer 8

TRUE

Question 9

Radiographic lesions: lung

Bacterial pneumonia

Pneumothorax

Answer 9

• Bacterial pneumonia (bronchopneumonia)
  
  • Ventral location
  • Localized or regional consolidation
  • Likely silhouettes with the heart and diaphragm
  • May progress to abscessation (mixed opacity nodules) and pleuritis (pleural fluid) = pleuropneumonia
• Pneumothorax
  
  • Trauma
    
    • Air collects in dorsal aspect of thoracic cavity

Question 10

Radiographic lesions: lung

Exercise-induced pulmonary hemorrage (EIPH)

Answer 10

• Occurs in most performance horses and goes undetected unless endoscopy done
• Some horses have epistaxis
• In a few, bleeding is severe enough to appear as inc. opacity in caudodorsal lung field
• Etiology
  
  • High pulmonary vascular pressure during max exercise
  • Neovascularization secondary to pulmonary inflammation
  • Coagulation dysfunction
  • Intrathoracic shear forces generated during exercise
  • Failure of lung to accomodate massive increase in CO to meet demands of high intensity exercise

Question 11

Radiographic lesions: lung

Chronic bronchitis

Answer 11

• Usually an allergic reaction
• COPD (heaves)
• Enhances bronchial conspicuity
  
  • Sometimes a tough call