Thoracic Imaging Flashcards
(30 cards)
What does the minor fissure separate?
The right upper lobe (RUL) from the right middle lobe (RML)
The minor fissure is visible in both frontal and lateral views as a fine horizontal line.
How are the major fissures visualized on radiographs?
Only on the lateral radiograph as oblique lines
If fluid-filled, the major fissures can appear as concave curvilinear opacities in the lateral hemithorax on the frontal view.
What does the major fissure on the right separate?
The right upper lobe (RUL) and right middle lobe (RML) from the right lower lobe
What does the major fissure on the left separate?
The left upper lobe (LUL) from the left lower lobe (LLL)
What is the Azygos lobe?
An accessory lobe in the right apex demarcated by the Azygos fissure
Present in less than 1% of individuals
How is the Azygos lobe formed?
Formed during fetal development when the cardinal vein penetrates the apex rather than passing around it, carrying both pleural layers with it.
The posterior cardinal vein is one of the precussors to the azygos vein
What does the superior accessory fissure seperate?
The superior and basal segments of the right lower lobe
Seen in approximately 5% of people
What does the inferior accessory fissure seperate?
The medial basal segment from all other segments
Can be in either long, most commonly the right
Seen in approximately 12% of people
What does the left minor fissure seperate?
The lingula from the left upper lobe
Seen in approximately 8% of people
What is atelectasis?
Loss of lung volume due to decreased aeration
Atelectasis is synonymous with collapse.
What are the main causes of atelectasis?
- Bronchial obstruction
- Mucus plugging
- External compression (e.g., small lung volumes, pleural effusions)
External compression can lead to atelectasis by reducing the space available for lung expansion.
What are direct signs of atelectasis?
- Displacement of the fissures
- Plate-like or triangular opacity from the collapsed lung
- Vascular crowding
Direct signs are observed from lobar volume loss.
What are indirect signs of atelectasis?
- Elevation of the diaphragm
- Rib crowding on the side with volume loss
- Mediastinal shift to the side with volume loss
- Overinflation of adjacent or contralateral lobes
- Hilar displacement
Indirect signs are due to the effect of volume loss on adjacent structures.
What is obstructive atelectasis?
Obstructive atelectasis occurs when alveolar gas is absorbed by blood circulating through alveolar capillaries but is not replaced by inspired air due to bronchial obstruction.
It can lead to lobar atelectasis, which is a complete collapse of a lobe.
How does supplemental oxygen affect obstructive atelectasis?
Obstructive atelectasis occurs more quickly when the patient is breathing supplemental oxygen since oxygen is absorbed from the alveoli more rapidly than nitrogen.
What is the most common cause of airway obstruction in children?
Aspirated foreign object.
What happens to the affected side in children with airway obstruction?
The affected side becomes hyperexpanded due to a ball-valve effect.
Ball-valve effect is where air is allowed to pass the FB on inspiration but not expiration leading to air trapping
What is subsegmental atelectasis?
Subsegmental atelectasis is a subtype of obstructive atelectasis commonly seen after surgery or general illness, due to mucus obstruction of the small airways.
What causes relaxation (passive) atelectasis?
Relaxation (passive) atelectasis is caused by relaxation of lung adjacent to an intrathoracic lesion causing mass effect, such as a pleural effusion, pneumothorax, or pulmonary mass.
What is adhesive atelectasis due to?
Adhesive atelectasis is due to surfactant deficiency.
In which conditions is adhesive atelectasis commonly seen?
Adhesive atelectasis is seen most commonly in neonatal respiratory distress syndrome and acute respiratory distress syndrome (ARDS).
What is cicatricial atelectasis?
Cicatricial atelectasis is volume loss from architectural distortion of lung parenchyma by fibrosis.
What is the characteristic finding of left upper lobe collapse on frontal view?
Veil-like opacity +/- Luftsichel sign
What is the luft sichel sign?
Crescent of air seen on the frontal radiograph
LUL collapse
It represents the interface between the aorta and the hyperexpanded superior segment of the left lower lobe.
