Unilateral hypertranslucent hemithorax has many potential causes. It may be the result of rotation away from an optimal position or because of pathology.
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. When the patient is turned to the right, the right side will be hypertranslucent.
- poor patient positioning
Where rotation isn't 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 defect
- Poland syndrome (absent pectoralis major muscle)
- surgical removal of pectoralis major muscle for flap surgery.
Pleura and pleural space
- airway obstruction
- bronchial compression (hilar mass, cardiomegaly)
- endobronchial obstruction with air trapping (foreign body, tumour, mucous plug)
- obliterative bronchiolitis
- Swyer-James syndrome
- pulmonary emphysema (asymmetric)
- congenital lobar overinflation (CLO) (previously called congenital lobar emphysema).
- unilateral bullus/bullae
- compensatory hyperinflation
- unilateral lung transplant: 'abnormal' side may be ipsilateral or contralateral, depending on the reason for transplantation
- 1. Collins J, Stern EJ. Chest radiology, the essentials. Lippincott Williams & Wilkins. (2007) ISBN:0781763142. Read it at Google Books - Find it at Amazon
- 2. Davies SG, Nakielny R. Aids to Radiological Differential Diagnosis. Saunders Ltd. (2009) ISBN:0702029793. Read it at Google Books - Find it at Amazon