Pneumoperitoneum
Every time you check a chest X-ray you should make sure there is no free intra-abdominal air under the diaphragm (pneumoperitoneum). This is a sign of bowel perforation.
Chest X-ray Abnormalities
Diaphragmatic abnormalities
Key points
- Do not miss a pneumoperitoneum
- An obscured hemidiaphragm may be due to adjacent lung disease
- An abnormal diaphragm position may indicate a serious pathology
Pneumoperitoneum on an erect chest X-ray
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Pneumoperitoneum on an erect chest X-ray
- The lungs are normal
- The diaphragm is crisply defined on both sides (arrowheads)
- Air under the diaphragm (asterisks) is seen as crescents of relatively low density (black)
- Black air can be seen on both sides of the bowel wall (blue line) – this is known as the double-wall sign or Rigler's sign (usually only seen on abdominal X-rays)
Clinical information
- Acute, severe abdominal pain
- Abdominal guarding on examination
- Risk factors for peptic ulceration included smoking, high alcohol intake, and long term use of non-steroidal anti-inflammatory drugs
Diagnosis
- Pneumoperitoneum – at laparotomy a perforated duodenal ulcer was found
Diaphragm contour abnormalities
The normal hemi-diaphragms form distinct dome-shaped contours against the adjacent lungs. If these contours are obscured it is often possible to determine the location of lung disease. For example, the lower lobes of both lungs lie directly in contact with each hemi-diaphragm. Consolidation of the lower lobes, therefore, obscures the crisp contour of the adjacent hemi-diaphragm.
Left lower lobe consolidation
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Left lower lobe consolidation
- The left hemidiaphragm is obscured (red line = normal position)
- Consolidation of the left lung base (highlighted area) extends behind the heart
Clinical information
- Cough, high temperature and raised white cell count
Diagnosis
- Left lower lobe pneumonia
Raised hemidiaphragm
The right hemi-diaphragm usually lies at a level slightly above the left. There are many possible causes of a raised hemidiaphragm such as damage to the phrenic nerve, lung disease causing volume loss, congenital causes such as a diaphragmatic hernia, or trauma to the diaphragm.
Diaphragmatic rupture
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Diaphragmatic rupture
- The left hemidiaphragm is not visible
- There is bowel in the lower half of the left hemi-thorax
- The mediastinum is displaced to the right
Clinical information
- History of severe chest trauma
Diagnosis
- Left hemi-diaphragmatic rupture with herniation of bowel into the left-hemithorax
Phrenic nerve palsy
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Phrenic nerve palsy
- Raised left hemidiaphragm (red to blue lines)
- Left upper zone mass contacts the mediastinum
Clinical information
- Known inoperable lung cancer
- Rapid worsening of shortness of breath
Diagnosis
- Left phrenic nerve palsy due to direct invasion of the nerve
Caution!
- Occasionally a raised hemidiaphragm may be mistaken for a pleural effusion
- They can have similar X-ray appearances and both can cause dullness to percussion, but only an effusion should be drained!
- A CT may be necessary prior to chest drain insertion if there is doubt