Pulmonary plethora is a term used to describe the appearances of increased pulmonary perfusion on chest radiographs. It is commonly used in pediatric radiology.
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Pathology
Usually a left-to-right shunt of 2:1 is required for pulmonary plethora to occur 2,3. Increased pulmonary perfusion occurs in a number of situations 1,2:
- left-to-right cardiac shunts, e.g. ASD, VSD, PDA
- partial or total anomalous pulmonary venous return
- transposition of the great arteries
- truncus arteriosus
- vein of Galen malformation
It may also been seen in healthy patients with increased cardiac output (e.g. pregnancy) 3.
Radiographic features
Plain radiograph
- prominent pulmonary vasculature
- pulmonary vessels are dilated and tortuous extending farther into the peripheral one-thirds of the lungs
- diameter of a pulmonary artery is greater than the accompanying bronchus
- increased size and number of hilar pulmonary arteries
- >3-5 end-on should be seen
- diameter of the right descending pulmonary artery is bigger than the diameter of the trachea
- cardiomegaly may be present
Practical points
Pulmonary plethora can occur with or without cyanosis with different causes attributed 3,4:
- without cyanosis: left-to-right shunt
- with cyanosis: transposition of great arteries, TAPVR, truncus arteriosus