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Basics Of Chest X Ray Part-6, The Lungs, Pleura And The Chest Wall.

Pulmonary Medicine Blog By Dr Deepu

Lung abnormalities mostly present as areas of increased density, which can be divided into the following patterns:

Consolidation
Atelectasis
Nodule or mass - solitary or multiple
Interstitial
Less frequently areas of decreased density are seen as in emphysema or lungcysts.

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Chest X-Ray - Lung disease.
Consolidation

Atelectasis


Nodule - Masses

Solitary pulmonary node 
Interstitial pattern


Interstitial lung diseases will be discussed in coming posts.

Pleura

Pleural fluid

It takes about 200-300 ml of fluid before it comes visible on an CXR (figure).
About 5 liters of pleural fluid are present when there is total opacification of the hemithorax.

Total opacification of the right hemithorax in a patient with pleuritis carcinomatosa on both sides.
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On the right there is only some air visible in the major bronchi creating an air bronchogram within the compressed lung.
Pleural fluid may become encysted.


Here we see fluid entrapped within the fissure.
This can sometimes give the impression of a mass and is called 'vanishing tumor'.

Pneumothorax

The table lists the most common causes of a pneumothorax.
The other cystic lungdisease which causes pneumothorax is Langerhans cell histiocytosis (LCH) which is seen in smokers.
Study the CXR.

There are two important findings.
The retracted visceral pleura is seen (blue arrow) which indicates that there is a pneumothorax.
There is a horizontal line visible (yellow arrow).

Normally there are no straight lines in the human body unless when there is an air-fluid level.
This means that there is a hydro-pneumothorax.
When a pneumothorax is small, this air-fluid level can be the only key to the diagnosis of a pneumothorax.
Study the CXR.
There are 3 important findings.
Notice that the mediastinum is slightly displaced to the left.
Does this mean that there is a tension pneumothorax?
Do you have an idea about the cause of the pneumothorax?
There is a hydropneumothorax.

Notice the air-fluid level (blue arrow).
The upper lobe is still attached to the chest wall by adhesions.
Maybe this patient was treated for a prior pneumothorax.
There is a lung cyst in the upper lobe (red arrow).
So we can assume that the pneumothorax has something to do with a cystic lung disease.
Since this patient is a woman, lymphangioleiomyomatosis (LAM) is a possible diagnosis.
LAM is a rare lung disease that results in a proliferation of smooth muscle throughout the lungs resulting in the obstruction of small airways leading to pulmonary cyst formation and pneumothorax.
LAM also occurs in patients who have tuberous sclerosis.
Study the CXR.

What is your diagnosis?
This is not a pneumothorax but a skin fold.
The radiography was performed supine with a CR cassette inserted underneath the patient, which resulted in a skinfold.
Notice that there are lung markings beyond the apparent pneumothorax.
Here two CXRs of another patient with obvious skinfolds.
Recognition of a pneumothorax depends on the volume of air in the pleural space and the position of the body.
On a supine radiograph a pneumothorax can be subtle and approximately 30% of pneumothoraces are undetected.
A sign to look for is the 'deep sulcus sign'.
It represents lucency of the lateral costophrenic angle extending toward the hypochondrium (Figure).
The image is of a patient in the ICU who is on mechanical ventilation. There was an acute exacerbation of the dyspnea.
There is a deep sulcus sign on the left
Notice that the left hemidiaphragm is depressed.
This is an important finding since it indicates a tension pneumothorax.
The image on the below is after insertion of an intercostal drain.
Notice that the diaphragm has regained its normal appearance.
Pleural opacities
The table lists the most common causes of pleural opacities.

Pleural plaques
The CXR shows multiple opacities.

They have irregular shapes and do not look like a lung masses or consolidations.
Some of these opacities are clearly bordering the chest wall (red arrows).
All these findings indicate that we are dealing asbestos related pleural plaques.
Asbestos related pleural plaques are usually:
bilateral and extensive.
covering the dome of the diaphragm.
Unilateral pleural calcifications are usually due to:

infection (TB)
empyema
hemorrhagic
Pleural hematoma

These images are of a patient, who had a pleural opacity after a chest trauma.
It was believed to be a hematoma and resolved spontaneously.

Chest wall

Ribfractures
The most common identified chest wall abnormalities are old ribfractures.
The CXR shows many rib deformities due to old fractures.

When a rib fracture heals, the callus formation may create a mass-like appearance (blue arrow).

Sometimes a CT is necessary to differentiate a healing fracture from a lung mass.
Notice the large lung volume and the enlarged pulmonary vessels.
Probably we are dealing with pulmonary arterial hypertension in a patient with COPD.
The second most common chest wall abnormalities that we see on a CXR are metastases in vertebral bodies and ribs.

Notice the expansile mass in the posterior rib on the right.

Abdomen

The most obvious finding on this CXR is free air under the diaphragm.
This finding indicates a bowel perforation, unless when the patient had recent abdominal surgery and there is still some air left in the abdomen, which can stay there for several days.
There is another subtle finding in the left upper lobe.
A subtle density projecting over the first rib - hidden area - proved to be a lungcarcinoma.
Here another patient with free abdominal air.

Notice the very thin regular line which is the diaphragm (arrow).

At first impression one might think that this is just some plate-like atelectasis due to poor inspiration.

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