Monday, June 28, 2010

Kerley's Line (Septal Line)

Kerley’s A line
An essentially straight linear opacity 2–6 cm long and 1–3 mm wide, usually situated in an upper lung zone, that points to the hilum centrally and is directed toward but does not extend to the pleural surface.
These are longer (at least 2cm) unbranching lines coursing diagonally from the periphery toward the hila in the inner half of the lungs. They are caused by distension of anastomotic channels between peripheral and central lymphatics of the lungs. Kerley A lines are less commonly seen than Kerley B lines. Kerley A lines are never seen without Kerley B or C lines also present.

Kerley’s B line

An essentially straight linear opacity 1.5–2 cm long and 1–2 mm wide, usually situated in the lung base and oriented at right angles to the pleural surface with which it is usually in contact peripherally.
These are short parallel lines at the lung periphery. These lines represent interlobular septa, which are usually less than 1 cm in length and parallel to one another at right angles to the pleura. They are located peripherally in contact with the pleura, but are generally absent along fissural surfaces. They may be seen in any zone but are most frequently observed at the lung bases at the costophrenic angles on the PA radiograph, and in the substernal region on lateral radiographs. Kerley B lines are seen in Congestive Heart Failure (CHF) and Interstitial Lung Diseases (ILD).

Kerley’s C line
A group of branching, linear opacities producing the appearance of a fine net, situated at the lung base and representing Kerley’s B lines seen en face.
These are the least commonly seen of the Kerley lines. They are short, fine lines throughout the lungs, with a reticular appearance. They may represent thickening of anastomotic lymphatics or superimposition of many Kerley B lines.



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