General Flashcards
Pulmonary Lobes
Right Upper Lobe Right Middle Lobe Right Lower Lobe Left Upper Lobe Left Lower Lobe
Right upper lobe segments
(AAP) clockwise
- Apical - Anterior - Posterior
Right middle lobe segment
- (LM) clockwise
- Lateral
- Medial
- Lateral
Right Lower Lobe Segment
(SM-PAL) going clockwise
- Superior
- Medial Basal
- Posterior Basal
- Anterior Basal
- Lateral Basal
Left Upper Lobe Segment
(ISAA) going clockwise
- Apical Posterior
- Apical Anterior
- Superior Lingula
- Inferior Lingula
Left Lower Lobe Segment
(SM-PAL) going clockwise
- Superior - Medial Basal - Posterior Basal - Anterior Basal - Lateral Basal
Azygous Fissure
Accessory fissure present in less than 1% of patients, seen in the presence of an azygos lobe. An azygos lobe is an anatomic variant where the right upper lobe apical or posterior segments are encased in their own parietal and visceral pleura
Atelectasis
Loss of lung volume due to decreased aeration
Synonymous with Collapse
Direct Signs of Atelectasis
Due to lobar volume loss and include:
- Displacement of the fissures
- Vascular crowding
Indirect Signs of Atelectasis
Due to the effect of volume loss on adjacent structures
- Elevation of the diaphragm - Rib crowding on the side the volume loss - Mediastinal shift to the side with volume loss - Over-inflation of adjacent or contralateral lobes - Hilar displacement
Air bronchograms are not seen in atelectasis when
The cause of the atelectasis is central bronchial obstruction, but air bronchograms can be seen in subsegmental atelectasis.
Subsegmental atelectasis
Is caused by obstruction of small peripheral bronchi, usually by secretions
What are the four mechanisms of atelectasis
ORCA
- Obstructive
- Relaxation
- Cicatricial
- Adhesive
When Does Obstructive Atelectasis Occur
Occurs when alveolar gas is absorbed by blood circulating through the alveolar capillaries but is not replaced by inspired air due to bronchial obstruction
Obstructive atelectasis occurs more quickly when the patient is breathing supplemental oxygen why?
Oxygen is absorbed from the alveoli more rapidly than nitrogen
In children airway obstruction is often due to aspirated foreign objects. What do you see on xray
In contrast to adults, the affected side becomes hyper-expanded in children due to the ball-valve effect
Subsegmental atelectasis is a subtype of obstructive atelectasis commonly seen after surgery or general illness
what is it due to?
Mucus obstruction of the small airways
What is relaxation/compressive atelectasis
-Atelectasis is caused by relaxation of the lung adjacent to an intrathoracic lesion causing mass effect, such as pleural effusion, pneumothorax, or pulmonary mass
What is adhesive atelectasis
-Due to surfactant deficiency. Most commonly seen in neonatal respiratory distress syndrome but can also be seen in ARDS
What is Cicatricial atelectasis
-Volume loss from architectural distortion of the lung parenchyma by fibrosis
Cause of Lobar Atelectasis
-Usually caused by central bronchial obstruction (obstructive atelectasis) which may be secondary to mucus plugging or an obstructing neoplasm
Pathology of Lobar Atelectasis on the basis of whether it is acute versus chronic
- If the lobar atelectasis occurs acutely, mucus plugging is the most likely cause
- If the lobar atelectasis is seen in an outpatient setting an obstructing central tumor must be ruled out
-Lobar atelectasis or collapse of an entire lobe has characteristic appearances depending on which of the five lobes is collapsed
Frontal Radiograph
The upper lobes go up
The right middle lobe compresses in
The lower lobe compresses medially
Lateral Radiograph
The upper and lower lobes form a superior and inferior sandwich and the right middle lobe forms a medial sandwich
Left upper lobe collapse
-The luftsichel (air-sickle in german) sign of left upper lobe collapse is a crescent of air seen on frontal radiograph which represents the interface between the aorta and the hyper expanded superior segment of the left lower lobe
Left lower lobe collapse:
In left lower lobe collapse, the heart slightly rotates and the left hilum is pulled down
The flat wrist sign describes the flattening of the left heart border as a result of downward shift of the hilar structures and resultant cardiac rotation
Right upper lobe atelectasis
The reverse S sign of Golden is seen in right upper lobe collapse caused by an obstructing mass. The central convex margins of the mass form a reverse S. Although the sign describes a reverse S, it is commonly known as Golden’s S sign. Similar to left upper lobe collapse, a right upper lobe collapse should raise concern for an underlying malignancy, especially with a Golden’s S sign present. The juxtaphrenic peak sign is a peridiaphragmatic triangular opacity cased by diaphragmatic traction from an inferior accessory fissure or an inferior pulmonary ligament
Right middle lobe atelectasis
The findings of right middle lobe atelectasis can be subtle on the frontal radiographs. Silhouetting of the right heart border by the collapsed medial segment of the middle lobe may be the only clue. The lateral radiograph shows a wedge shaped opacity anteriorly
Right lower lobe atelectasis
Right lower lobe atelectasis is the mirror image of left lower atelectasis
The collapsed lower lobe appears as a wedge shaped retrocardiac opacity
What is round atelectasis
- Round atelectasis is focal atelectasis with a round morphology that is always associated with adjacent pleural abnormality such as (PPP)
- pleural effusion
- pleural thickening or plaque
- pleural neoplasm
Where is round atelectasis most common
Round atelectasis is most common in the posterior lower lobes
What Are the five diagnoses that are required to diagnosis round atelectasis
- Adjacent pleura must be abnormal
- Opacity must be peripheral and in contact with the pleura
- Opacity must be round or elliptical
- Volume loss must be present in the affected lobe
- Pulmonary vessels and bronchi leading into the opacity must be curved-this is the comet tail sign
What is the elemental unit of lung function
The secondary pulmonary lobule (SPL) is the elemental unit of lung function
What does each SPL contain
Each SPL contains a central artery (centrilobular artery) and a central bronchus, each branching many times to ultimately produce acinar arteries and respiratory bronchioles
What is the acinus
Basic unit of gas exchange, containing several generations of branching respiratory bronchioles, alveolar ducts, and alveoli
How many acini for secondary lobule unit
There are generally 12 or fewer acini per secondary lobule
Connective Tissue that encases each SPL is called
Interlobular Septa
Thickening of the interlobular Septa can be from
Enlargement of either the venous or lymphatic spaces
