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Intravascular air and CT
  1. W-J Lee,
  2. K-L Liu,
  3. S-J Chen
  1. Department of Medical Imaging, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan
  1. Dr S-J Chen, Department of Medical Imaging, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan; james_5586{at}hotmail.com

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Dr Ku and co-workers wrote an interesting article describing a patient with air emboli in the superior vena cava surrounding a central venous catheter (CVC) and bilateral pulmonary opacities recognised on contrast enhanced chest CT.1 The round pulmonary opacity was noted on chest radiograph soon after insertion of the CVC. From these findings, they suggest that this is a rare case of venous air pulmonary infarction mimicking round pneumonia. However, further evidence should be obtained to support this assumption.

CT is highly sensitive for the detection of small amounts of intravascular air, which can be found in the central veins in up to 23% of patients on contrast-enhanced CT and it rarely results in symptoms unless there is a right to left shunt.24 It is introduced during insertion of the venous catheter or more frequently accidental injection of air during intravenous injections (fig 1).

Figure 1 Air bubble trapped around the central venous catheter in the inferior vena cava (arrow) was incidentally noted on non-enhanced CT scan of the abdomen.

Normal lung tissue receives dual blood supply from pulmonary and bronchial arteries. Pulmonary infarct is infrequent after acute obstruction of the pulmonary artery because the bronchial circulation plays an important role in preserving lung tissue.5 In about 15% cases of acute pulmonary embolism, the collateral supply by bronchial arteries is insufficient. Pulmonary infarcts may be observed several hours later.4

The small air bubbles in the superior vena cava may originate from intravenous contrast media injection during CT scan and round pneumonia is a reasonable diagnosis of pulmonary opacities in this case.

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