Pleural space

Question 1

Pleural anatomy

Answer 1

• Parietal
  
  • Covers the entire inner surface of the thorax
  • Divided into 3 parts:
    
    • Costal
    • Diaphragmatic
    • Mediastinal
• Visceral
  
  • Covers lung parenchyma
• Left and right pleural sacs are closed
• Pleural space is a potential space
• Contains some fluid that lubricates lung and thoracic body wall
• Space is in the area between
  
  • Individual lung lobes
  • Lung lobes and body wall

Question 2

Radiographic anatomy

Answer 2

• Normal pleura is usually not visible
  
  • Silhouettes with adjacent soft tissue
  • Too thin to absorb enough x-rays to be detected
  • Except if radiographed tangentially
• Occasionally, thin soft-tissue/fluid opaque pleural lines are noted between lobes
  
  • Pleura may be thick
  • Pleura may be in line w/ beam and absorb enough x-rays
  • Cannot determine exact reason but slight pleural thickening is usually of little significance
• Location of pleural fissures, the regions between lung lobes, is an important radiographic-anatomic feature
• Pleural fissure lines will vary with
  
  • Positioning or recumbency of the patient
  • Amount of fluid present
  • Tangential alignment of normal pleura w/ x-ray beam

Question 3

Pleural disease

Clinical signs?

Cats?

Thoracic auscultation?

Resp. pattern?

Answer 3

• Clinical signs for pleural fluid include:
  
  • Dyspnea, thoracic cavity distention, dyssynchronous breathing
• In cats, breathing is slower and more deliberate than in dogs
• Thoracic auscultation reveals muffled lung sounds over the affected regions
• The resp. pattern is the same whether air, fluid, or abdominal contents are in the pleural space

Question 4

What are the 3 main categories of pleural disease?

Answer 4

• Pleural effusion
  
  • Fluid in pleural space
    
    • Cannot be distinguished
• Pneumothorax
  
  • Gas in pleural space
    
    • Enters from outside, mediastinum, or lung
• Diaphragmatic hernias

Question 5

Pleural effusion: clinical significance

Answer 5

• Primary pleural disease is rare
  
  • Often a sign of disorder elsewhere
• ALWAYS IMPORTANT–requires workup
• If detected with peritoneal effusion: indicates severe disease with a poor prognosis

Question 6

Pleural effusion: DDx

Answer 6

• CHF
• Malignancy
• Pyothorax
• Pneumonia
• Trauma
• Coagulopathy
• Rib tumor
• Diaphragmatic hernia
• Chylothorax
• Mediastinitis

Question 7

Pleural effusion: what do radiographic signs depend on?

Answer 7

• Volume of fluid
• Patient positioning
• Distribution of fluid
• Free vs. loculated fluid

Question 8

Free pleural effusion (11 thingz)

Answer 8

• Radiograph signs are the same for dif. types of fluids
• Gravity
• Lung compliance
• Appearance will be different in dif. views
• Wide interlobular fissures
• Soft tissue opacity between lungs and thoracic wall
• Retraction of lungs from thoracic wall
• “Scalloping” of lung margins
• Silhouetting of heart in DV view
• Silhouetting of diaphragm
• Soft tissue opacity dorsal to sternum

Question 9

Pleural effusion: wide interlobar fissures

Answer 9

• Thickness and # depend on amount of fluid present and position of the patient
• Min of 100mL of fluid must be present to detect fissure lines in MBD
• X-ray must strike the intralobar tangentially
• In cases of small amounts of fluid, interlobar fissures are more likely to be detected on VD and laterals

Question 10

Important positioning concept w/ pleural effusions

Answer 10

• Gravity is in play
• Fluid will migrate to dependent regions

Question 11

Pleural effusions: restrictive pleuritis

Answer 11

• Signs of pleural fusion
• Severely rounded lung lobe margins due to changed lung compliance
• Lung lobes do not return to normal space following thoracocentesis

Question 12

Pleural effusions: atypical or asymmetrical distributions

Answer 12

• Usually uniform distribution
• If non-uniform displacement, consider:
  
  • Lung pathology altering compliance of the lung
  • Mass in thoracic wall
  • Loculated fluid
• Pyothorax is a common cause of unilateral distributions of pleural fluid

Question 13

Pleural effusion: other tests

Answer 13

• Horizontal-beam radiograph
• Other view to look for inciting lesions
  
  • If large amounts of fluid are present remove before continuing further imaging studies
• Ultrasound +/- FNA
• CT

Question 14

Pitfalls of pleural effusion

Answer 14

• Thickened pleura
• Mineralized costal cartilage
• Thoracic wall deformity

Question 15

Pneumothorax: classifications

Answer 15

• Open
  
  • Free communication between pleural space and environment
• Closed
  
  • Air leaks into pleural space via lung, bronchi, trachea, esophagus, or mediastinum
• Tension
  
  • Valve, continuous influx of air upon inspiration that does not return to lung on expiration
  • Pleural pressure > atmospheric pressure
• Normotensive
  
  • Pleural pressure = atmospheric pressure

Question 16

Pneumothorax: clinical significance

Answer 16

• Traumatic is the most frequent type and result in a normotensive closed
  
  • Young, males predisposed
• May be open due to gunshot wound or penetrating foreign body
• Spontaneous type occurs more frequently in deep-chested breeds
• Small pneumothorax w/o clinical signs will not require treatment
• Pneumothorax due to lung disease will likely require intervention
• Usually occurs bilaterally
• Air moves easily between right and left sides
• Unilateral can occur for similar reasons as unilateral pleural effusions

Question 17

Pneumothorax: DDx

Answer 17

• Trauma
• Lung rupture
• Ruptured pulmonary bulla
• Chest wall rent
• Pulmonary emphysema
• Extension of a pneumomediastinum
• Rupture of a cavitary lung mass
• Iatrogenic barotrauma

Question 18

Pneumothorax: radiographic signs

Answer 18

• Gas opacity between lungs and thoracic wall
• Pulmonary blood vessels do not continue to thoracic wall
• Retraction of lungs from thoracic wall
• Lung is small and has increased opacity
• Appearance of dorsal displacement of heart on lateral view (“loss of sternal contact”)
• Best seen on lateral view
• Easier seen on DV versus VD

Question 19

Tension pneumothorax: radiographic signs

Answer 19

• Greater degree of lung collapse
• Tenting of diaphragm
• “Barrel-chested”

Question 20

Pitfalls of pneumothorax

Answer 20

• Skin folds
  
  • Soft tissue bands extend beyond pulmonary limits and into chest wall
  • May need hot light to see pulmonary vessels
• Breed variations
  
  • Chondrodystrophic breeds
  • Chest conformation
• Miscellaneous
  
  • Small cardiac silhouette
  • Hyperinflated lungs

Question 21

Pneumothorax: other tests

Answer 21

• Horizontal beam radiography
  
  • Lateral recumbency
• CT
  
  • Test of choice to find bullae
  • Greater sensitivity than rads