Unilateral hypertranslucent hemithorax

Last revised by Dr Mohamed Tofeig on 21 Sep 2021

Unilateral hypertranslucent hemithorax has many potential causes. It may be the result of rotation away from an optimal position or because of pathology.

Rotation

A unilateral hypertranslucent hemithorax may be caused by the positioning of the patient. Rotation away from the radiation beam alters the attenuation of the beam differently on either side of the thorax. The rotated side has shorter tissue distance which increases the x-ray transmission that passes through it. When the patient is turned to the right, the right side will be hypertranslucent. 

Rarely, grid cutoff may also mimic a unilateral hypertranslucency.

Pathology

Where rotation is not thought to be the cause of the differential transradiancy, it may be useful to consider the potential causes by the structures they involve, in the order in which the radiation beam hit them. The age of the patient is also a factor that should be considered.

A helpful mnemonic is SAFEPOEM.

Chest wall defects - muscle abnormalities
Pleura and pleural space
Mediastinal
Pulmonary (ventilation)
Vascular (perfusion)
See also

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Cases and figures

  • Case 1: mastectomy
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  • Case 2: compensatory hyperinflation
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  • Case 3: pneumothorax
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  • Case 4: Poland syndrome
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  • Case 5: Heimlich valve and hemopneumothorax
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  • Case 6: re-expansion pulmonary edema
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  • Case 7: Swyer-James syndrome
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  • Case 8: pneumothorax
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