Ch.5 - Recognizing Atelectasis

Question 1

Subsegmental atelectasis usually occurs in patients who…?

Answer 1

Are NOT taking a deep breath (splinting) and produces horizontal linear densities, usually at the lung bases.

Question 2

Compressive atelectasis occurs passively when the lung is …?

Answer 2

Collapsed by poor inspiration (at the bases), or from a large, adjacent pleural effusion or pneumothorax.
When the underlying abnormality is removed, the lung usually expands.

Question 3

Round atelectasis is …?

Answer 3

A type of passive atelectasis in which the lung does NOT re-expand when a pleural effusion recedes, usually due to pre-existing pleural disease.
–> May produce a masslike lesion that can mimic a tumor on CXR.

Question 4

Obstructive atelectasis occurs …?

Answer 4

Distal to an occluding lesion of the bronchial tree because of reabsorption of the air in the distal airspaces via the pulmonary capillary bed.

Question 5

Important point about obstructive atelectasis?

Answer 5

Produces consistently recognizable patterns of collapse based on the assumptions that the visceral and parietal pleura invariably remain in contact with each other and every lobe of the lung is anchored at or near the hilum.

Question 6

Signs of obstructive atelectasis include:

Answer 6

1. Displacement of the fissures.
2. Increased density of the affected lung.
3. Shift of the mobile structures of the thorax toward the atelectasis.
4. Compensatory hyperinflation of the unaffected ipsilateral or contralateral lung.

Question 7

Atelectasis tends to resolve quickly when …?

Answer 7

If it occurs acutely.

The more chronic the process, the longer it takes to resolve.

Question 8

What is COMMON to ALL forms of atelectasis?

Answer 8

Loss of volume in some or all of the lung –> Increased density of the lung involved.

Question 9

4 main signs of atelectasis:

Answer 9

1. Displacement of the major/minor fissures.
2. Increased density of the atelectatic portion of lung.
3. Shift of the mobile structures in the thorax, ie, the heart, trachea, and/or hemidiaphragm.
4. Compensatory overinflation of the unaffected segments, lobes, or lung.

Question 10

At least … cm of the right heart border normally projects to the right of the spine on a NON ROTATED frontal radiograph.

Answer 10

1cm.

Question 11

A slight RIGHTWARD deviation of the trachea is always present at the site of the left-sided …?

Answer 11

AORTIC KNOB.

Question 12

In about …% of normal people the left hemidiaphragm is HIGHER than the right.

Answer 12

10%.

Question 13

How can we see the COMPENSATORY OVERINFLATION of the unaffected ipsilateral lobes or the contralateral lung?

Answer 13

This may be noticeable on the lateral projection by an increase in the size of the retrosternal clear space and on the frontal projection by extension of the overinflated contralateral lung across the midline.

Question 14

Subsegmental atelectasis is also called?

Answer 14

Discoid atelectasis or platelike atelectasis.

Question 15

Subsegmental atelectasis produces?

Answer 15

LINEAR densities of varying thickness usually PARALLEL to the diaphragm, most commonly at the lung BASES.

Question 16

Subsegmental atelectasis occurs most commonly?

Answer 16

In patients who are “splinting”, i.e., not talking a deep breath, such as post-op patients or patients with pleuritic chest pain.

Question 17

On a single study, WITHOUT prior exam for comparison, subsegmental atelectasis can look identical to what?

Answer 17

Chronic, linear scarring.

Question 18

Subsegmental atelectasis typically disappears within a matter of?

Answer 18

DAYS. Scarring remains.

Question 19

Compressive atelectasis?

Answer 19

Loss of volume due to passive compression of the lung.

Question 20

When caused by POOR INSPIRATORY EFFORT, passive atelectasis may mimic what?

Answer 20

Airspace disease at the BASES.

Question 21

Pitfall about compressive atelectasis?

Answer 21

Be suspicious of compressive atelectasis if the patient has taken LESS THAN an 8 posterior-rib breath –> Check the LATERAL projection for confirmation of the presence of real airspace at the BASE.

Question 22

Round atelectasis?

Answer 22

A form of compressive atelectasis.

Question 23

Round atelectasis is usually seen?

Answer 23

At the PERIPHERY of the lung BASE.

Question 24

Round atelectasis usually develops?

Answer 24

From a combination of prior pleural disease (such as asbestos exposure or TB) + The formation of a pleural effusion that produces adjacent compressive atelectasis.

Question 25

A fibrothorax is produced following?

Answer 25

Complete REMOVAL of the lung.

Question 26

Mechanism of round atelectasis?

Answer 26

When the pleural effusion recedes, the underlying pleural disease leads to a portion of the atelectatic lung becoming TRAPPED. This produces a masslike lesion that can be confused for a tumor.

Question 27

Round atelectasis on CT?

Answer 27

The bronchovascular markings characteristically lead for the round atelectasis back to the hilum –> A comet-tail appearance.

Question 28

How long does it take for the air in obstructive atelectasis to be resorbed?

Answer 28

18-24hrs for an ENTIRE lung to collapse with the patient breathing room air BUT LESS THAN AN HOUR with the patient breathing 100% O2.

Question 29

In general, how do the lungs collapse?

Answer 29

In a FANLIKE configuration with the base of the fan-shaped triangle anchored at the pleural surface and the apex of the triangle anchored at the hilum.

Question 30

Pitfall about atelectasis?

Answer 30

The more atelectatic a lobe or segment becomes (that is, the smaller its volume), the LESS VISIBLE it becomes on the CXR.
–> This can lead to the FALSE assumption of improvement when, in fact, the atelectasis is worsening.

Question 31

Right upper lobe atelectasis - On the FRONTAL radiograph?

Answer 31

1. Upward shift of the MINOR FISSURE.

2. Rightward shift of the TRACHEA.

Question 32

Right UPPER lobe atelectasis - On the LATERAL radiograph?

Answer 32

Upward shift of the MINOR fissure and a FORWARD SHIFT of the major fissure.

Question 33

S sign of Golden?

Answer 33

If right upper lobe atelectasis is produced by a large enough mass in the RIGHT HILUM, the combination of the hilar mass + the upward shift of the MINOR fissure produces a characteristic appearance on the FRONTAL radiograph = S sign of Golden.

Question 34

Left upper lobe atelectasis - On the frontal radiograph?

Answer 34

1. Hazy are of INCREASED density around the LEFT hilum.
2. There is a LEFTWARD shift of the trachea.
3. There may be elevation with “tenting” (peaking) of the left hemidiaphragm.
4. Compensatory hyperinflation of the lower lobe may cause the superior segment of the left lower lobe to extend to the APEX of the thorax of the AFFECTED side.

Question 35

Left lower lobe atelectasis - On the LATERAL radiograph?

Answer 35

Forward displacement of the MAJOR fissure + the opacified upper lobe forms a band of increased density running roughly parallel to the STERNUM.

Question 36

Lower lobe atelectasis - On the FRONTAL radiograph?

Answer 36

1. BOTH the right and left lower lobes collapse to form a TRIANGULAR density that extends from its apex at the hilum to its base at the medial portion of the affected hemidiaphragm.
2. Elevation of the hemidiaphragm on the affected side.
3. Heart may shift toward the side of the volume loss.
4. On the right (only), there is a downward shift of the MINOR fissure.

Question 37

Lower lobe atelectasis - On the LATERAL radiograph?

Answer 37

DOWNWARD + POSTERIOR displacement of the MAJOR FISSURE until the completely collapsed lower lobe forms a small triangular density at the posterior costophrenic angle.

Question 38

In the critically-ill patient, atelectasis occurs most frequently in the …?

Answer 38

LEFT LOWER LOBE.

Question 39

How will left lower lobe atelectasis manifest?

Answer 39

By disappearance (silhouetting) of all or part of the left hemidiaphragm. Always check that the left hemidiaphragm is seen in its entire extent.

Question 40

Right middle lobe atelectasis - On the FRONTAL radiograph?

Answer 40

1. Triangular density with its base silhouetting the right heart border and its apex pointing toward the lateral chest wall.
2. Minor fissure is displaced downward.

Question 41

Right middle lobe atelectasis - On the LATERAL radiograph?

Answer 41

1. Triangular density with its base directed ANTERIORLY and its apex AT THE HILUM.
2. Minor fissure may be displaced INFERIORLY and the major fissure SUPERIORLY.

Question 42

4 MCCs of OBSTRUCTIVE atelectasis?

Answer 42

1. Tumors.
2. Mucous plugs.
3. Foreign body aspiration.
4. Inflammation.

Question 43

The 3 most commonly observed types of atelectasis are:

Answer 43

1. Subsegmental atelectasis (also known as discoid or plate-like atelectasis).
2. Compressive or passive atelectasis.
3. Obstructive atelectasis.