Chest x-ray anatomy
Soft tissues
The soft tissues are often overlooked when viewing a chest x-ray, however, abnormalities of the soft tissue may give important clues to a diagnosis. Whenever you look at a chest x-ray, have a look at the soft tissues, especially around the neck, the thoracic wall, and the breasts.
If a patient has very thick soft tissue due to obesity, underlying structures such as the lung markings may be obscured. Large breasts may obscure the costophrenic angles, giving the impression of the presence of pleural effusions.
Key points
- Assess the soft tissues on every chest x-ray
- Thick soft tissue may obscure underlying structures
- Black within soft tissue may represent gas
Hover over image to show findings
Breast asymmetry
Here the breasts are asymmetric. The underlying lung markings (white boxes) appear denser on the left than the right. This should not be mistaken for underlying lung disease.
Breast asymmetry is very common, even to the extent that no breast tissue is visible on one side. It should not be assumed that the patient has had a mastectomy, unless this is known from the history.
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Hover over image to show findings
Nipple markings
The nipples are clearly seen on this chest x-ray, but care is needed whenever there is a chance that the markings may represent underlying lung nodules. If there is any doubt then a repeat chest x-ray should be performed, with metallic markers used to indicate the position of the nipples.
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Hover over image to show findings
Pseudo-blunting of the costophrenic angle
At first glance the left costophrenic angle appears blunt. This is because the patient was in a rotated position when the x-ray was taken. This has resulted in a greater thickness of breast overlying the costophrenic angle on the left, compared to the right.
If you are not careful you may be misled into thinking there is a pleural effusion or other pathology causing costophrenic angle blunting.
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Hover over image to show findings
Soft tissue fat
This close-up demonstrates a normal fat plane between layers of muscle. Fat is less dense than muscle and so appears blacker.
Note that the edge of fat is smooth. Irregular areas of black within the soft tissues may represent air tracking in the subcutaneous layers. This is known as surgical emphesyma.
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Assessing the soft tissues
The soft tissues can be misleading. As well as hiding genuine pathology, normal soft-tissues may give the appearance of disease.
If you are in doubt, the first thing to do is examine the patient. If clinically important a repeat x-ray or another investigation may be required.