The hidden abnormality

Published on 23/05/2015 by admin

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Last modified 22/04/2025

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CHAPTER 11 The hidden abnormality

11.1 Pancoast’s tumour 154

11.2 Hiatus hernia 156

11.3 Air under the diaphragm 158

11.1 Pancoast’s tumour

At first glance it may be hard to spot that there is an abnormality on this film. Note, however, the increased whiteness at the right apex. On the magnified image you should also be able to see that the right second rib has fractured – a pathological fracture. This appearance is of a Pancoast’s tumour with invasion into the chest wall.

A number of abnormalities can be easily missed. Before deciding an X-ray is normal:

1. Look carefully at the apices of both lungs. This is a common site for lung pathology, for example a Pancoast’s tumour or chronic fibrosis. Lesions here can be easily missed because the apex of the lung is hidden by ribs and clavicles.

2. Look carefully at the heart shadow. Lesions behind the heart are often missed because they are obscured by the whiteness of the heart. Look carefully for any parts of the heart shadow that look whiter than the rest. Look also for the triangular shadow of left lower lobe collapse and other subtle changes such as consolidation behind the heart.

3. Look carefully at the mediastinum. Changes in the shape of the mediastinum can be very subtle.

4. Look at the hilum. Changes in the shape or density of the hilum can be easily missed.

5. Obtain a lateral film – some abnormalities are more obvious on the lateral.

6. Read the radiologist’s report!

11.2 Hiatus hernia

This is the film of a 67-year-old patient who complained of a chronic cough. You can see a curved white line lying behind the heart. This is a hiatus hernia. When questioned, the patient complained of mild heartburn with no other symptoms.

When scanning an apparently normal X-ray it is important to look behind the heart. The heart is usually a fairly uniform white colour and areas of increased whiteness can indicate possible pathology. Therefore if you see an area of increased whiteness behind the heart:

1. Decide whether it has any of the characteristics of the white lung field described previously. For example can you see an air bronchogram which would suggest consolidation or the tramline or ring-like shadows which would suggest bronchiectasis?

2. Look carefully at the shadowing to see whether it has the appearance of left lower lobe collapse. This is described on page 52 and has the appearance of a dense white triangle behind the heart. It is easy to miss so you should look carefully for this.

3. Look to see whether the appearance is consistent with a hiatus hernia. Look for the outline of the stomach which may appear as a rounded white line either behind the heart or next to the left heart border. Look for the flat line of a fluid level which you occasionally see and is caused by fluid within the stomach.

11.3 Air under the diaphragm

This is the X-ray of a 72-year-old man who presented to casualty acutely unwell with abdominal and chest pain. Examination revealed a silent abdomen. Note the areas of blackness immediately under the diaphragms (arrowed). This represents air collecting under the diaphragm and confirms the clinical suspicion of abdominal perforation. Subsequent history-taking revealed that he had a 2-year history of recurrent upper abdominal pain and on surgery a perforated gastric ulcer was found.

Finish your examination of the chest X-ray by looking at the area under the diaphragm. The area immediately under the diaphragm will usually be white since the upper part of the abdomen contains the dense structures of the liver and spleen. Because of this you can usually only make out the upper surface of the diaphragm. You may see a darker round area under the left hemidiaphragm. This is the air bubble within the stomach.

One of the main reasons for looking under the diaphragm is to detect the presence of free air. This is an important sign since it indicates intra-abdominal perforation. Other intra-abdominal pathologies you might see include areas of calcification (small areas of increased whiteness) under the right diaphragm corresponding to gallstones, and dilated loops of bowel under the left diaphragm.

The chest X-ray is a very sensitive investigation for the detection of free abdominal air since it can detect as little as 10 ml. It appears as a rim of blackness immediately under the diaphragm and you will recognize this since it may enable you to see both the upper and lower surface of the diaphragm.

It is sometimes difficult to differentiate air under the diaphragm from the normal stomach bubble. If in doubt then look at the following:

1. Look at the thickness of the diaphragm, that is the line between the blacker area below and the lungs above. If there is free air immediately below the diaphragm, then the white line between the air and the chest will appear very thin since it will consist of the diaphragm only. If the air is in the stomach then the white line created will consist of both stomach lining and diaphragm and appear thicker. In general, if the line is less than 5 mm, then free air is probably present.

2. Look at the length of the air bubble, that is, the distance from its medial to lateral aspect. If it is longer than half the length of the hemidiaphragm it is likely to be free air, since air within the stomach is restricted by the anatomy of the stomach.

3. Look at both hemidiaphragms. If air is present below the right and left hemidiaphragms, it is likely to be free air in the abdomen.

4. If you are still in doubt order a decubitus film. This is taken with the patient lying on their left side. Free air will rise away from the diaphragm and come to lie lateral to the liver in the uppermost aspect of the abdomen whereas air within the stomach will remain in the same position. Remember that it takes over 10 minutes for these changes to occur so the patient needs to be on their side for 10 minutes before the X-ray is taken.

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