Upper lobe pulmonary venous diversion (also described as cephalisation of the pulmonary veins) reflects elevation of left atrial pressure and is an early sign of pulmonary edema.
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Clinical presentation
The normal left atrial pressure is 5-10 mmHg. An elevation of left atrial pressure to 10-15 mmHg will result in upper lobe venous diversion. Typically, the cause for that increase in left atrial pressure is left heart failure (most commonly), or mitral valve disease 1.
Radiographic features
On frontal chest radiograph, it is seen as dilation of the upper lobe pulmonary veins as they branch superiorly from the hilum. This can be measured objectively, with cephalisation present if the upper lobe veins are of the same or higher diameter than the lower lobe veins, measured equidistant from the hilar point 2.