Flattening of the diaphragm

Last revised by Dr Daniel J Bell on 16 May 2021

Flattening of the diaphragm is the most sensitive sign on chest radiographs for the presence of hyperinflation of the lungs, usually due to emphysema 1,2.

On a lateral chest radiograph, the normal dome of each hemidiaphragm should rise at least 1.5 cm above a line connecting the costophrenic angle posteriorly and sternophrenic angle anteriorly 1.

On a frontal chest radiograph, the normal dome of each hemidiaphragm should rise at least 1.5 cm above a line connecting the costophrenic angle laterally and cardiophrenic angle medially 1.

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Cases and figures

  • Figure 1: flattening of the diaphragm measurement
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  • Case 1: marked hyperinflation
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