Thoracic wall and diaphragm

Question 1

Diaphragm anatomy

Answer 1

• Musculotendinous partition
• Major muscle contributor to respiration
• Large surface area assists in the lymphatic drainage of the abdomen
• Attaches at the ventral aspect of L3-4
• 2 crura and large capula (body)
• 3 openings which allow aorta (hiatus), vena cava (foramen), nerves, esophagus (hiatus), thoracic duct, and azygos

Question 2

Radiographic anatomy

Answer 2

• Diaphagm is uncommonly detected as a separate radiographic entity
• To be detected it requires that adjacent structures must be of dif. opacities
• More commonly only the most ventral portion is detected as it is adjacent to the falciform ligament
• Several normal anatomical variations are poss.
  
  • Cats do not follow the rules
  • Many reasons: breed, age, obesity, respiration, gravity, beam/animal positioning

Question 3

How are the right and left lateral views different?

What species breaks the rules?

What can cause crus to differ?

Answer 3

• Right
  
  • R crus more cranial
  • CVC enters most cranial crus
  • Crus more parallel
• Left
  
  • L crus more cranial
  • CVC crosses over cranial crus and enters caudal one
  • Crura are divergent
  • Fundus of stomach caudal to L crus
• Not reliable in cats (assholes)
• Obesity and disease might affect crura

Question 4

DV and VD views

Answer 4

• In VD you may detect 1, 2, or 3 dome-shaped structures assoc. w/ the diaphragm
• Depends on beam centering
• In DV usually only 1

Question 5

Diaphragmatic lesions

Answer 5

• Hernias
  
  • Diaphragmatic
    
    • Acquired
    • Congenital
      
      • Peritonealpericardial diaphragmatic
      • Hiatal
      • Gastroesophageal intussusception
• Hernias may be detected incidentally

Question 6

Diaphragmatic hernias

Answer 6

• Abdominal viscera protrudes through the diaphragm
• Most common cause = trauma
• May/may not result in clinical signs
  
  • Dyspnea, abdominal pain, vomiting, regurg, muffled heart sounds, weak femoral pulse
  • May have concurrent pleural fluid
• Rads may be diagnostic
• Other diagnostic imaging modalities
  
  • Ultrasound
  • Barium study

Question 7

Traumatic DH–radiographic signs

Answer 7

• Abdominal viscera in pleural space
• Displacement of abdominal structures
• Displacement of thoracic structures
  *

Question 8

Congenital abnoramalities: peritonealpericardial diaphragmatic hernia (PPDH)

Answer 8

• Round cardiac silhouette
• Heterogenous opacity (fat/gas) of cardiac silhouette
• Silhouetting of heart and diaphragm
• Can be assoc. w/ sternal abnormality
• Usually incidental finding

Question 9

Congenital abnormalities: hiatal hernia

Answer 9

• Portion of stomach enters thorax through esophageal hiatus
• 2 types:
  
  • Sliding
  • Paraesophageal
• May be assoc. w/ esophageal reflux
• Often manifests in patients w/ partial upper airway obstruction
• Most common to see in L lateral view but not in R or VD
• May have to give barium to confirm (but usually not due to classic changes in conspicuity with position)

Question 10

Thoracic wall anatomy

Answer 10

• Intercostal muscle
• Fat
• Nerves
• Ribs
• Thoracic vertebrae
• Blood vessels
• Skin
• Parietal pleura
• Sternebrae
• Often ignored; critical part of the assessment/evaluation of the thorax

Question 11

Pitfalls of thoracic wall anatomy

Answer 11

• Mineralization of cartilaginous portion as dogs age
  
  • Can be seen early in very young dog
• Once mineralized (stiff) can form exuberant calcificdations around the costochondral jx
  
  • Can be confused with tumors, infection or lung nodules

Question 12

Thorax: radiographic anatomy

Answer 12

• Pedunculated soft-tissue nodules attached to the skin may appear as nodules in the lung parenchyma
  
  • Nodules are very distinct
  • May need additional views
  • Can apply contrast to area and retake radiograph

Question 13

Thoracic congenital abnormalities

Answer 13

• Changes in number, shape/position of ribs vertebrae, sternebrae are not uncommon
  
  • Agenesis
  • Hypoplasia
  • Bilateral or unilateral

Question 14

Thoracic congenital abnormalities: pectus excavatum

Answer 14

• Mild to severe dorsal placement of the caudal sternebrae
• Results in reduced size of thoracic cavity
• Displacement of the heart
• Occasionally seen in cats, rare in dogs

Question 15

3 thoracic wall lesions?

Answer 15

• Trauma
• Rib tumors
• Soft tissue tumors

Question 16

Thoracic wall masses

Answer 16

Sometimes hard to tell thoracic wall masses from lung masses (intrapulmonary or extrapleural)