The Radiology Assistant - Lung Disease
The Radiology Assistant - Lung Disease
The Radiology Assistant - Lung Disease
Lung disease
Four-Pattern Approach
Robin Smithuis
Radiology Department of the Rijnland Hospital, Leiderdorp, the Netherlands
Publicationdate 2014-02-01
On a chest x-ray lung abnormalities will either present as areas of increased density or as areas of
decreased density.
Lung abnormalities with an increased density - also called opacities - are the most common.
At the end we will also discuss diseases that present as areas of decreased density.
4-Pattern approach
Consolidation
Differential diagnosis
Lobar consolidation
Diffuse consolidation
Multifocal
Interstitial disease
Differential diagnosis on HRCT
UIP
Interstitial pneumonias
Atelectasis
Lobar atelectasis
Rounded atelectasis
Nodules and Masses
Solitary Pulmonary Nodule
Fleischner Society recommendations for follow-up of nodules
Multiple masses
Mucoid impaction
Decreased density or lucencies
Cavitation
Pneumatocele
4-Pattern approach
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Whenever you see an area of increased density within the lung, it must be the result of one of these
four patterns.
1. Consolidation - any pathologic process that fills the alveoli with fluid, pus, blood, cells
(including tumor cells) or other substances resulting in lobar, diffuse or multifocal ill-defined
opacities.
2. Interstitial - involvement of the supporting tissue of the lung parenchyma resulting in fine or
coarse reticular opacities or small nodules.
3. Nodule or mass - any space occupying lesion either solitary or multiple.
4. Atelectasis - collapse of a part of the lung due to a decrease in the amount of air in the alveoli
resulting in volume loss and increased density.
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Here are the most common examples of these four patterns on a chest x-ray (click image to
enlarge).
Consolidation
Lobar consolidation
Diffuse consolidation
Multifocal ill-defined consolidations
Interstitial
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You have to realize that it is not always possible to divide lung abnormalities into one of these four
patterns, but that should not be a problem.
Sometimes you are confronted with an abnormality that looks like a mass, but it could also be a
consolidation.
Just do the work-up of both the differential diagnosis of masses and consolidation.
In such a case information from clinical data, old films or follow-up films and CT-scan will usually
solve the problem.
Consolidation
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Consolidation is the result of replacement of air in the alveoli by transudate, pus, blood, cells or
other substances.
The disease usually starts within the alveoli and spreads from one alveolus to another.
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Differential diagnosis
The table summarizes the most common diseases, that present with consolidation.
Click to enlarge.
A way to think of the differential diagnosis is to think of the possible content of the alveoli:
1. Water - transudate.
2. Pus - exsudate.
3. Blood - hemorrhage.
4. Cells - tumor, chronic inflammation.
Another way to think of consolidation, is to look at the pattern of distribution:
Diffuse - perihilar (batwing) or peripheral (reversed batwing).
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Lobar or focal.
Multiple - usually multiple ill-defined densities.
Now it is obvious that some diseases can have more than one pattern.
For instance a lobar pneumonia caused by streptococcus pneumoniae may become diffuse if the
patient does not respond to the treatment.
Other examples are organizing pneumonia (OP) and chronic eosinophilic pneumonia.
These diseases typically present as multifocal consolidations, but sometimes they may become
diffuse.
OP is organizing pneumonia. When it is idiopathic it is called cryptogenic (COP). The old name is
BOOP - Bronchiolitis Obliterans Organizing Pneumonia.
It is very important to differentiate between acute consolidation and chronic consolidation, because
it will limit the differential diagnosis.
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Lobar consolidation
The most common presentation of consolidation is lobar or segmental.
Lobar pneumonia
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At the borders of the disease some alveoli will be involved, while others are not, thus creating ill-
defined borders.
As the disease reaches a fissure, this will result in a sharp delineation, since consolidation will not
cross a fissure.
As the alveoli that surround the bronchi become more dense, the bronchi will become more visible,
resulting in an air-bronchogram (arrow).
In consolidation there should be no or only minimal volume loss, which differentiates consolidation
from atelectasis.
Expansion of a consolidated lobe is not so common and is seen in Klebsiella pneumoniae and
sometimes in Streptococcus pneumoniae, TB and lung cancer with obstructive pneumonia.
Lobar pneumonia
Lobar pneumonia
On the chest x-ray there is an ill-defined area of increased density in the right upper lobe without
volume loss.
In the proper clinical setting this is most likely a lobar or segmental pneumonia.
However if this patient had weight loss or long standing symptoms, we would include the list of
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Based on the images alone, it is usually not possible to determine the cause of the consolidation.
Other things need to be considered, like acute or chronic illness, clinical data and other non-
pulmonary findings.
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Hemorrhage post-biopsy
Hemorrhage
In this case there was a solitary nodule in the right upper lobe and a biopsy was performed.
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Lung infarction
The radiographic features of acute pulmonary thromboembolism are insensitive and nonspecific.
The most common radiographic findings in the Prospective Investigation of Pulmonary Embolism
Diagnosis (PIOPED) study were atelectasis and patchy pulmonary opacity.
The peripheral consolidation is seen in the region of the emboli and can be attributed to hemorrhage
in the infarcted area.
Pulmonary sequestration
Pulmonary sequestration
It is a congenital abnormality.
A nonfunctioning part of the lung lacks communication with the bronchial tree and receives arterial
blood supply from the systemic circulation.
Patients present with recurrent infection when bacteria migrate through the pores of Kohn.
Notice the feeding artery, that branches off from the aorta (blue arrow).
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Diffuse consolidation
The most common cause of diffuse consolidation is pulmonary edema due to heart failure.
This is also called cardiogenic edema, to differentiate it from the various causes of non-cardiogenic
edema.
The increased heart size is usually what distinguishes between cardiogenic and non-cardiogenic.
Look for other signs of heart failure like redistribution of pulmonary blood flow, Kerley B-lines and
pleural fluid.
However some patients, who have an acute cardiac infarction, may still have a normal heart size,
while other patients who have a large heart due to a chronic heart disease, may have non-cardiac
pulmonary edema due to a superimposed pulmonay infection, ARDS, near-drowning etc.
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You probably would like to look at old films to see if there are any changes.
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Unlike lobar pneumonia, which starts in the alveoli, bronchopneumonia starts in the airways as acute
bronchitis.
The disease does not cross the fissures, but usually starts in multiple segments.
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The chest x-ray shows diffuse consolidation with 'white out' of the left lung with an air-bronchogram.
The disease started as a persitent consolidation in the left lung and finally spread to the right lung.
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It demonstrates, that based on the x-ray alone, it is not certain which pattern we are looking at.
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On the other hand this also could be areas of consolidation with hypodense areas due to necrosis.
Finally the diagnosis non Hodgkin's disease was made based on biopsy.
Batwing
The sparing of the periphery of the lung is attributed to a better lymphatic drainage in this area.
Reverse Batwing
Multifocal
Multifocal consolidations are also described as multifocal ill-defined opacities or densities.
As mentioned before bronchopneumonia starts in the bronchi and then spreads into the
lungparenchyma.
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In some cases however the underlying pathology of multiple ill-defined densities is interstitial
disease, like in the alveolar form of sarcoidosis in which the granulomas are very small and fill up
the alveoli.
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The larger ones are ill-defined and maybe there is an air-bronchogram in the right lower lobe.
Probably we are dealing with multifocal consolidations, but one might also consider the possibility of
multiple ill-defined masses.
This patient had a several month history of chronic non-productive cough, that did not respond to
antibiotics.
The lab-findings were normal which makes bronchoalveolar carcinoma and lymphoma less likely.
Biopsy revealed the diagnosis of organizing pneumonia (OP) also known as BOOP.
Wegener's granulomatosis
Wegener's is a collagen vascular disease with vasculitis involving the lung, kidney and sinuses.
In the lung the vasculitis causes infarcts which first present as ill-defined areas of consolidation.
In a later stage these infarcts become more circumscribed and can be seen as multiple nodules or
masses, sometimes with cavitation.
There are ill-defined densities in the right lung, which proved to be a manifestation of Wegener's.
Interstitial disease
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Most of our knowledge about imaging findings in interstitial lung disease comes from HRCT.
On HRCT there are four patterns: reticular, nodular, high and low attenuation (table).
On a Chest X-Ray it can be very difficult to determine whether there is interstitial lung disease and
what kind of pattern we are dealing with.
When the cysts have thick walls like in Langerhans cell histiocytosis or honeycombing, it frequently
presents as a reticular pattern on a CXR.
However sometimes an interstitial pattern can be seen and in many cases UIP can be suspected
based on the x-ray findings.
It can be difficult to determine whether we are dealing with a reticular pattern or a cystic pattern.
This creates a reticular pattern on the chest x-ray, because the cysts in honeycombing have thick
walls.
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Kerley B lines are 1-2 cm long horizontal lines near the lateral pleura.
Here another chest x-ray with interstitial edema and Kerley B lines in a patient with congestive heart
failure.
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Sometimes the reticulation is more coarse like in this case of congestive heart failure.
Sarcoidosis
In this case the chest x-ray shows subtle findings that could be described as fine reticulation.
In many cases a HRCT is needed to determine the exact nature of the findings.
The HRCT - not shown - demonstrated a fine nodular appearance as a result of sarcoidosis.
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Longstanding Sarcoidosis
Here a typical chest film in a patient with long standing Sarcoidosis (stage IV).
The differential diagnosis includes chronic hypersensitivity pneumonitis, which also results in fibrosis
with upper lobe predominance.
These are called conglomerate masses, which are the result of conglomerates of nodules.
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UIP
UIP is a histologic pattern of pulmonary fibrosis.
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On a chest X-ray UIP manifests as a reticular pattern particularly at the lung bases.
This pattern was first attributed to chronic congestive heart failure, but persisted on follow-up CXR's
despite therapy.
The CXR demonstrates a reticular interstitial pattern with a preference at the lung bases.
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PCP
Interstitial pneumonias
An acute reticular pattern is most frequently caused by interstitial edema due to cardiac heart
failure.
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Sarcoidosis
On a CXR sarcoidosis usually first presents with hilar and mediastinal lymphadenopathy (example).
Parenchymal disease can present as consolidation or even as masses, but the most common
presentation is a fine nodules.
Lymphangitis carcinomatosis
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Atelectasis
Atelectasis or lung-collapse is the result of loss of air in a lung or part of the lung with subsequent
volume loss due to airway obstruction or compression of the lung by pleural fluid or a
pneumothorax.
Evidently it is very important to recognize the various presentations of atelectasis, since some of
them can be easily misinterpretated.
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Lobar atelectasis
Lobar atelectasis or lobar collaps is an important finding on a chest x-ray and has a limited
differential diagnosis.
The illustration summarizes the findings of the different types of lobar atelectasis.
Findings:
1. triangular density
2. elevated right hilus
3. obliteration of the retrosternal clear space (arrow)
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On the PET-CT a lungneoplasm is seen with subsequent atelectasis of the right upper lobe due to
obstruction of the upper lobe bronchus.
A common finding in atelectasis of the right upper lobe is 'tenting' of the diafphragm (blue arrow).
This patient had a centrally located lungcarcinoma with metastases in both lungs (red arrows).
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A pectus excavatum can mimick a middle lobe atelectasis on a frontal view, but the lateral view
should solve this problem.
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Chest x-rays of a 70-year old male who fell from the stairs and has severe pain on the right flank.
The right interlobar artery is not visible, because it is not surrounded by aerated lung but by the
collapsed lower lobe, which is adjacent to the right atrium.
On a follow-up chest film the atelectasis has resolved. We assume that the atelectasis was a result
of post-traumatic poor ventilation with mucus plugging.
Notice the reappearance of the right interlobar artery (red arrow) and the normal right heart border
(blue arrow).
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The CT-images demonstrate the atelectasis of the left upper lobe (blue arrow).
There is a centrally located mass which obstructs the left upper lobe bronchus (red arrow).
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You would not expect the apical region to be this dark, but in fact this is caused by overinflation of
the lower lobe, which causes the superior segment to creep all the way up to the apical region.
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Since the silhouette of the right heart border is still visible, there is probably partial atelectasis of
the lower lobe and not of the middle lobe.
Lungcarcinoma on the left obstructing the upper lobe bronchus and also a lung carcinoma on the right obstructing
the right lower lobe.
On the PET-CT there is both a tumor in the left lung, aswell as in the right.
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This is comparable to the golden-S sign in right upper lobe atelectasis and is suspective of a
centrally obstructing mass.
In this case there is compensatory overinflation of the left lower lobe resulting in a normal position
of the diaphragm and the mediastinum.
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The contour of the left diaphragm is lost when you go from anterior to posterior.
We cannot see the lower lobe vessels, because they are surrounded by the atelectatic lobe.
Normally when you follow the thoracic spine form top to bottom, the lower region becomes less
opaque.
Total atelectasis
The chest x-ray shows total atelectasis of the right lung due to mucus plugging.
A common cause of total atelectasis of a lung is a ventilation tube that is positioned too deep and
thus obstructing one of the main bronchi.
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These images are of a patient who had widespread bronchopneumonia and was on ventilation.
After suction of the mucus plug the left lung was re-aerated.
The chest x-ray shows a nearly total opacification of the left hemithorax.
Unlike most of the above cases, which were caused by obstruction, in this case the atelectasis is a
result of compression.
The compression of the lung by the loculated fluid collections is best seen on the CT-image (blue
arrow).
The CT-scan was performed, because the patient was suspected of having pulmonary emboli (red
arrow).
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Rounded atelectasis
The typical findings of rounded atelectasis on CT are pleural thickening, pleural-based mass and
comet tail sign.
The theory is that a local pleuritis causes the pleura to thicken and contract.
The distorted vessels appear to be pulled into the mass and resemble a comet tail (4).
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Rounded atelectasis
Many would have a lungcancer on the top of their differential diagnostic list.
However there is also some pleural thickening (red arrow) and vessels seem to swirl around the
mass (blue arrows).
Whenever you see a pleural-based lesion that looks like a lungcancer, also consider the possibility of
rounded atelectasis.
Rounded atelectasis is a benign lesion and when the findings are convincing, then biopsy is not
needed.
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On the lateral film however the boundaries seem to be sharp, which is in favor of a mass.
Although a peripheral lungcancer is on top of our list, we now also consider the possibility of
rounded atelectasis.
Rounded atelectasis
There is an oval mass, pleural thickening and a comet tail sign (arrow).
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Plate-like atelectasis due to poor inspiration in a patient who had abdominal surgery
Plate-like atelectasis
Plate-like atelectasis is a common finding on chest x-rays and detected almost every day.
They are characterized by linear shadows of increased density at the lung bases.
They are usually horizontal, measure 1-3 mm in thickness and are only a few cm long.
In most cases these findings have no clinical significance and are seen in smokers and elderly.
They are seen in patients, that are in a poor condition and who breathe superficially, for instance
after abdominal surgery (figure).
Plate-like atelectasis is frequently seen in patients in the ICU due to poor ventilation.
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Platelike atelectasis is also frequently seen in pulmonary embolism, but since it is non-specific, it is
not a helpful sign in making the diagnosis of pulmonary embolism.
Cicacitration atelectasis
Here we have a patient who was treated with radiotherapy for lungcancer.
Notice the increased density of the lung tissue and the volume loss.
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Here we have a patient with atelectasis of the right upper lobe as a result of TB.
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A solitary pulmonary nodule or SPN is defined as a discrete, well-marginated, rounded opacity less
than or equal to 3 cm in diameter.
It has to be completely surrounded by lung parenchyma, does not touch the hilum or mediastinum
and is not associated with adenopathy, atelectasis or pleural effusion.
The differential diagnosis of SPN is basically the same as of a mass except that the chance of
malignancy increases with the size of the lesion.
Lesions smaller than 3 cm, i.e. SPN's are most commonly benign granulomas, while lesions larger
than 3 cm are treated as malignancies until proven otherwise and are called masses.
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In lesions that do not respond to antibiotics, probably the most important non-invasive diagnostic
tool is nowadays the PET-CT.
PET-CT can detect malignancy in focal pulmonary lesions of greater than 1 cm with a sensitivity of
about 97% and a specificity of 78%.
False-positive findings in the lung are seen in granulomatous disease and rheumatoid disease.
False negatives are seen in low grade malignant tumors like carcinoid and alveolar cell carcinoma
and lesions of less than 1 cm.
If so, no further follow up is necessary, with the exception of pure ground-glass lesions on CT scans,
which can be slower growing.
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For lesions with a benign pattern of calcification, further testing is not necessary.
Multiple masses
The differential diagnostic list of multiple masses is very long.
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Metastases
HRCT will demonstrate the random distribution unlike other diseases that have a perilymphatic or
centrilobular distribution.
The images show a renal cell carcinoma that has invaded the inferior vena cava with subsequent
spread of disease to the lungs.
Here another patient with widespread pulmonary metastases of a cancer, that was located in the
tongue.
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Mucoid impaction
Mucoid impaction
Mucus plugs or mucoid impaction can mimick the appearance of lung nodules or a mass.
Mucoid impaction is commonly seen in patients with bronchiectasis, as in cystic fibrosis (CF) and
allergic bronchopulmonary aspergillosis (ABPA).
ABPA is a hypersensitivity disorder induced by Aspergillus, that occurs in patients with asthma or CF.
In this case there are some mass-like structures in the right lung.
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The mucus in the dilated bronchi looks like the fingers in a glove.
Bronchial atresia
Bronchial atresia
The hyperinflation of the affected lungsegment is caused by collateral ventilation through the pores
of Kohn.
The characteristic finding is a hyperlucent area of the lung surrounding a branching or nodular
opacity that extends from the hilum.
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Radiologists use many terms to describe areas of decreased density or lucencies within the lung, like
cyst, cavity, pneumatocele, emphysema, bulla, honeycombing, bleb etc.
This makes it difficult to use these terms, since in many cases when we describe a chest X-ray, we
are trying to figger out what the pathology could be.
A more practical approach is to describe areas of decreased density in the lung as:
Cavity - lucency with a thick wall
Cyst - lucency with a thin wall
Emphysema - lucency without a visible wall
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We will discuss them here, because the prominent feature is the lucency.
Cavities can heal and end up as lungcysts and lungcysts can become infected and turn into thick
walled cavities.
Sometimes emphysematous bullae have visible walls that measure less than 1 mm.
Cysts usually contain air, but occasionally contain fluid or solid material.
The term is mostly used to describe enlarged thin-walled airspaces in patients with
lymphangioleiomyomatosis or Langerhans cell histiocytosis.
Thicker-walled honeycomb cysts are seen in patients with end-stage fibrosis (11).
Cavitation
Pneumonia
In virulent pyogenic infections an abscess may form within the consolidated lung as a result of
necrosis due to vasculitis and thrombosis.
When some of the pus is coughed up, a cavity can be seen on the chest film.
In granulomatous infection like TB, cavities may form, but these patients are usually not that ill.
Cavitation is not seen in viral pneumonia, mycoplasma and rarely in streptococcus pneumoniae.
Within one month after treatment with antibiotics, there was almost complete resolution of the
consolidation and the cavity.
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Pneumonia
At one year follow up only minimal changes are seen on the CXR.
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TB
In 5% of infected individuals the immunity is inadequate and clinically active disease develops,
which is known as progressive primary disease (9).
On the CXR it is seen as consolidation with cavitation in the apical segments of the upper and lower
lobes.
Here a patient with postprimary TB with cavitaty formation in the left upper lobe.
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Postprimary TB
TB
Continue...
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9/8/21, 11:07 PM The Radiology Assistant : Lung disease
Same patient
In the left upper lobe there is probably some traction-bronchiectasis due to the fibrosis.
Nontuberculous mycobacteria
Nontuberculous mycobacteria, also known as atypical mycobacteria, are all the other mycobacteria
which can cause pulmonary disease resembling TB.
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9/8/21, 11:07 PM The Radiology Assistant : Lung disease
Here a patient with active disease in both upper lobes due to infection with atypical mycobacterium.
Notice the air-fluid level indicating pus within the cavity (arrow).
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9/8/21, 11:07 PM The Radiology Assistant : Lung disease
Septic emboli
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9/8/21, 11:07 PM The Radiology Assistant : Lung disease
CT demonstrates more lesions than the chest film and can suggest the diagnosis in the proper
clinical setting by demonstrating wegde-shaped peripheral lesions abutting the pleura, air-
bronchograms within the ill-defined nodules and a feeding vessel sign (7).
Some argue whether there is really something like a feeding vessel sign (8).
The chest film shows two ill-defined densities iin the left lung, which are probably consolidations.
On the CT cavitation is seen and another density with cavitation in the right lung.
Septic emboli
Same patient.
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9/8/21, 11:07 PM The Radiology Assistant : Lung disease
Lungcancer
Bronchoalveolar carcinoma, or now called adenocarcinoma in situ, may occasionally cavitate and
sometimes present as multiple lesions.
Here a chest x-ray of a large cavitating lung cancer, which started as a small mass.
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9/8/21, 11:07 PM The Radiology Assistant : Lung disease
Lung infarction
The pulmonary embolus has caused a triangular density on the chest film (arrow).
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9/8/21, 11:07 PM The Radiology Assistant : Lung disease
Lung infarction
Same patient.
One year later there is a thick wall probably as a result of secondary infection.
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9/8/21, 11:07 PM The Radiology Assistant : Lung disease
Pneumatocele
The term pneumatocele is used to describe a lungcyst, which is most frequently caused by acute
pneumonia, trauma, or aspiration of hydrocarbon fluid and is usually transient.
6. Guidelines for Management of Small Pulmonary Nodules Detected on CT Scans: A Statement from the
Fleischner Society
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9/8/21, 11:07 PM The Radiology Assistant : Lung disease
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