Disease of the Mediastinum, Chest Wall, and Diphragm

Question 1

Is the mediastinum a closed space?

Answer 1

no, it communicates with the cervical soft tissue and retroperitoneal space.
It is separate from the pleural space, but fenestration allow for communication

Question 2

Where is the sternal LN located?

Answer 2

in the ventral mediastinal space

Question 3

What the the sternal LN drain?

Answer 3

diaphragm, pericardium, ventral thoracic and abdominal walls, peritoneal cavity

Question 4

What are some ddx for increased mediastinal size?

Answer 4

• mass
• esophageal enlargement
• fluid

Question 5

What are some causes of pneumomediastinum?

Answer 5

• tracheal rupture: GA with ET tube and positive pressure ventilation, trauma, foreign body
• lung trauma/ overinflation/ rupture of alveoli

Question 6

Can pneumothorax cause pneumomediastinum?

Answer 6

no, but if pneumomediastinum is severe, can lead to pneumothorax

Question 7

What’s the clinical signs of pneumomediastinum?

Answer 7

• usually nothing – can look really bad in CXR, but does not lead to respiratory distress unless there is concurrent pleural or pulmonary disease

Question 8

What’s the treatment for pneumomediastinum?

Answer 8

nothing, should spontaneous resolve within 2 weeks if there is no on-going cause

Question 9

What are the clinical signs associated with mediastinitis?

Answer 9

• tachypnea (likely due to pain)
• dyspnea
• cough
• head and/or neck edema
• regurgitation

Question 10

What are some differentials for mediastinal mass?

Answer 10

• cyst: more common in older cats, cystic (fluid filled), more caudally located, likely incidental finding
• lymphadenopathy:
  if tracheobronchial: lymphoma, fungal,
  if sternal: abdominal disease
• neoplasia:
  LSA - young, FeLV positive cats
  chemodectoma - heart-based mass

Question 11

What are some clinical signs associated with neoplasia in the mediastinum?

Answer 11

• coughing
• dyspnea
• dysphagia
• regurgitation
• edema of the head/neck, and/or forelimb
• less common: Horner’s, laryngeal nerve paralysis
• think of paraneoplastic lesions

Question 12

What cell type is frequently found in thymoma?

Answer 12

mast cells

Question 13

What’ the pathophysiology of thymic hemorrahge?

Answer 13

• could be related to thymic involution
• often seen in young <2y
• not uniformly fatal but most have died

Question 14

What are some clinical signs thymic hemorrahge?

Answer 14

• lethargy
• signs of thoracic pain
• increased respiratory effort
• dyspnea

Question 15

What’s a flail chest?

Answer 15

at least 2 consecutive ribs are fractured dorsal and ventrally
- results in paradoxical movements: moves in during inhalation, out during exhalation

Question 16

What other abnormalities can be seen on CXR for rib neoplasia?

Answer 16

pleural effusion

Question 17

What are some clinical signs associated with pectus excavatum?

Answer 17

• a lot are asymptomatic
• some have exercise intolerance, tachypnea, cyanosis, respiratory distress, and cardiac murmur

Question 18

What’s the most common disease of of the diaphragm?

Answer 18

traumatic rupture
- abdominal viscera displaced into the thoracic cavity

Question 19

What’s the most common organ to be herniated from the abdomen to the thorax?

Answer 19

liver

Question 20

What are some clinical signs of diaphragmatic herniation?

Answer 20

not all patients will have respiratory signs
- respiratory compromise
- dyspnea
- coughing
- exercise intolerance
- lethargy
- pleural effusion