Airway

Question 1

Most common primary tracheal malignancies?

Answer 1

• SCC, usually in distal trachea
• cylindroma(adenoid cystic carcinoma) usually in upper posterior trachea

Question 2

Normal tracheal wall thickness and diameter?

Answer 2

• Trachea 2cm in diameter
• Wall 2-3mm thick

Question 3

Approach to tracheal abnormalities?

Answer 3

Focal vs Diffuse

(1) Focal: stenosis, primary tumors, invasion/metastases
(2) Diffuse: Saber-Sheath trachea, polychondritis, GPA, amyloidosis, others(e.g. TB, aspergillosis, sarcoidosis, tracheoronchopathia osteochondroplastica)

Question 4

Common cause of tracheal stenosis and the mechanisms?

Answer 4

Prior intubation due to

(1) intraluminal masses i.e. granulation tissue
(2) collapse due to destructed tracheal rings & fibrosis

Question 5

CT feature of tracheal stenosis?

Answer 5

hourglass-shaped narrowing of trachea

Question 6

Cause of Saber-Sheath trachea?

Answer 6

trauma of chronic cough with breakdown of trachea rings in COPD patients

Question 7

CT features of Saber-Sheath trachea? How to differentiate from polychondritis?

Answer 7

1. Saber-Sheath trachea
   - normal thickness of racheal wall
   - side to side narrowing of INTRATHORACIC trachea
   - anteroposterior diameter preserved/increased
2. Polychondritis
   - thickened anterior & lateral tracheal walls(where the cartilage is)
   - narrowed both INTRATHORACIC and EXTRATHORACIC trachea

Question 8

CT features of tracheal involvement in granulomatosis with polyangiitis?

Answer 8

• thickened tracheal wall(commonly subglottic) and narrowed lumen
• collapsed trachea on expiration
• main bronchi can be involved

Question 9

CT features of tracheal involvement in amyloidosis?

Answer 9

• diffuse/multifocal thickening and narrowing of trachea & main bronchi
• calcification

Question 10

DDx of DIFFUSE trachea narrowing?

Answer 10

• TB
• scleroma
• invasive tracheobronchial aspergillosis
• sarcoidosis
• tracheobronchopathia osteochondroplastica
• Saber-Sheath trachea
• polychondritis
• granulomatosis with polyangiitis
• amyloidosis

Question 11

Is the presence of internal diameter of bronchus > artery means bronchiectasis?

Answer 11

• can be present in > 60 years old healty individuals / live at altitude
• true bronchiectasis also has THICKENED bronchial wall due to inflammation

Question 12

Pathophysiology of tree-in-bud sign? Common and uncommon causes?

Answer 12

• Mucus or pus-filled dilated centrilobular bronchioles
  1. Common causes
• bacterial bronchopneumonia
• chronic airway infection associated with bronchiectasis
• endobronchial spread of TB
• Mycobacterium avium complex infection
• fungal/viral infections
  2. Less common
• noninfectious inflammatory bronchiolitis i.e. follicular bronchiolitis
• mucoid impaction of bronchioles
• aspiration
• invasive mucinous adenocarcinoma

Question 13

Associations of lower lobe bronchiectasis?

Answer 13

• immune deficiency
• childhood infections
• ciliary dysmotility e.g. Kartagener syndrome

Question 14

Association of upper lobe bronchiectasis?

Answer 14

TB

Question 15

Association of bronchiectasis in middle lobe & lingula?

Answer 15

Mycobacterium avium complex infection

Question 16

Assocation of bronchiectasis in central(parahilar) lung regions?

Answer 16

• allergic bronchopulmonary aspergillosis
• cystic fibrosis(also in bilateral upper lobes)

Question 17

Appearance classification of bronchiectasis?

Answer 17

• cylindrical
• varicose
• cystic(associate with air-fluid level in dilated bronchi)

but of little significance

Question 18

Why mucous plugs are of higher attenuation than soft tissue?

Answer 18

presence of calcium or metallic ions

Question 19

What is small airway?

Answer 19

<3mm, lack cartialge in their walls (i.e. bronchiole)

Question 20

What is mosaic perfusion/attenuation and its pathophysiology?

Answer 20

• differences in lung parenchymal attenuation with patchy & geographic areas of relative lucency
• pulmonary vessels appear smaller in the relatively lucent lung regions
• most common (1) in small airway obstruction resulting in vasoconstriction & reduced blood flow (2)vascular occlusion e.g chronic pulmonary embolism

Question 21

Presence of mosaic perfusion/air trapping + absent findings of cellular bronchiolitis = ?

Answer 21

usually due to constrictuve/obliterative bronchiolitis(causes: infections, inhalation of toxic fumes, collagen vascular disease, drugs, chronic lung transplant rejection, graft-versus-host disease on bone marrow transplant)