Learning objectives
To understand the spectrum and pathophysiology of numerous possible causes of unilateral hypertranslucent hemithorax.
To describe some of their associated radiological signs on chest radiography and computed tomography (CT) in order to provide an appropriate differential diagnosis.
Background
On chest radiography,
unilateral hyperlucency is described as a darker appearance of one side of the thorax,
due to increased x-ray transmission.
It is an uncommon finding that could not have clinical relevance,
being the result of technical factors or wrong positioning,
but could also be the radiological expression of various pathology,
either congenital or acquired,
ranging from benign to potentially life-threatening diseases.
The first step in the evaluation is to check on radiologic technique and positioning,
since the most common causes of a unilateral...
Findings and procedure details
TECHNICAL/EXTERNAL FACTORS
When looking for excluding an hypertranslucent hemithorax due to faulty radiologic technique one must look to the relative exposure of soft tissues in the affected side,
especially of the lateral ribs or around the shoulder girdles.
Chest radiography-Fig. 3
Anode heel effect:
Anode heel effect refers to the intensity of the x-ray beam,
produced from the X-ray tube,
which is not uniform in all portions of the beam,
being comprised of central rays and diverging beams.
The rays towards the cathode end of...
Conclusion
In the approach of unilateral hemithorax hyperlucency,
technical and positional factors have to be excluded first,
and then pathology may be considered,
thinking that the decrease in pulmonary density may be the result from a combination of changes in the relative amounts of air,
blood,
and interstitial tissue,
and bychanges on any of the anatomic structures traversed by the x-rays.
PROPOSED DIAGNOSTIC ALGORITHM
It may also be usefull touse a mnemonicfor easy memorizing of unilateral hypertranslucent hemithoraxdifferential diagnosis,e.g.:
Personal information
João Diogo OLIVEIRA,Radiology Resident,
Department of Radiology,
Centro Hospitalar Lisboa Ocidental E.P.E.
Portugal.
Ana Coutinho SANTOS,Radiology Resident,
Department of Radiology,
Centro Hospitalar Lisboa Ocidental E.P.E.
Portugal.
Isa MARTINS, Radiologist,
Department of Radiology,
Centro Hospitalar Lisboa Ocidental E.P.E.
Portugal.
References
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Analysis: One Lung Looks Blacker.
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Collins J,
Stern EJ.
Unilateral Hyperlucent Hemithorax.
In: Chest Radiology: The Essentials.
Philadelphia,
PA: Lippincott Williams & Wilkins,2008:238-242
Reed JC.
Hyperlucent Thorax.
In: Chest Radiology: Plain Film Patterns andDifferential Diagnoses.
Philadelphia,
PA: Elsevier Mosby,
2011:349-365.
Brant WE,
Helms CA; Methods of examination,
normal anatomy,
and radiographic findings of chest disease In: Fundamentals of diagnostic radiology 4th edition; ,
Wolters Kluwer/Lippincott Williams & Wilkins...