Chest X-ray Level 2 Tutorial: Congestive Heart Failure
Tutorial: Congestive Heart Failure
Learn an approach to CHF findings on chest x-ray
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Tutorial: Congestive Heart Failure Kerley lines
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Kerley lines
Spoiler alert: Kerley lines are not curley. I know, I know ... don't get me started. Kerley lines are named after the Irish radiologist Sir Peter J. Kerley.

Kerley lines are caused by fluid in the interstitial septa of the lungs. They are also called septal lines. When seen on CT scans they are called septal thickening.

Due to increased hydrostatic pressure in the vessels due to heart failure, fluid will escape the vessels and enter the institial spaces of the lung and cause Kerley lines.

There are a few different types of Kerley lines, but they are all caused by the same mechanism of increased hydrostatic pressure. All Kerley lines are very skinny (< 1 mm thick) and straight.


Kerley A lines in constrast are "central" and radiate away from the hila of the lung. They are 2-5 cm long. They will cross vessel markings.

Kerley B lines are the most commonly described. They are in the periphery of the lung and aim straight into (and touch) the pleura. They are 1-2 cm long and you have to look hard to see them.

Kerley C lines are neither central nor peripheral. They are 2-3 cm long. They do not radiate away from the hila either.

In the x-ray below:
  • yellow arrows = Kerley A
  • blue arrows = Kerley B
  • red arrows = Kerley C


Congestive heart failure is not the only cause of thickened septal lines in the lung. They can also be caused by cancer spreading in the lymphatics, interstitial pneumonias (viral, mycoplasma and PJP), and pulmonary fibrosis to name a few other causes.