Septal lines in lung

Septal lines, also known as Kerley lines, are seen when the interlobular septa in the pulmonary interstitium become prominent. This may be because of lymphatic engorgement or oedema of the connective tissues of the interlobular septa. They usually occur when pulmonary capillary wedge pressure reaches 20-25 mmHg.

Kerley A lines

These are 2-6 cm long oblique lines that are <1 mm thick and course towards the hila. They represent thickening of the interlobular septa that contain lymphatic connections between the perivenous and bronchoarterial lymphatics deep within the lung parenchyma. On chest radiographs they are seen to cross normal vascular markings and extend radially from the hilum to the upper lobes. HRCT is the best modality for the demonstration of Kerley A lines.

Kerley B lines

These are thin lines 1-2 cm in length in the periphery of the lung(s). They are perpendicular to the pleural surface and extend out to it. They represent thickened subpleural interlobular septa and are usually seen at the lung bases. 

Kerley C lines

Kerley C lines are short lines which do not reach the pleura (i.e. not B or D lines) and do not course radially away from the hila (i.e. not A lines).

Kerley D lines

Kerley D lines are exactly the same as Kerley B lines, except that they are seen on lateral chest radiographs in the retrosternal air gap 2

Causes

Kerley lines are named after Sir Peter J. Kerley (1900-1979), an Irish radiologist who in addition to describing the interstitial lines now known as Kerley lines, also attended to King George VI 3-4

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Article Information

rID: 1552
System: Chest
Section: Signs
Synonyms or Alternate Spellings:
  • Kerley A lines
  • Kerley B lines
  • Kerley C lines
  • Kerley D lines
  • Kerley lines
  • Septal lines

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Cases and Figures

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    Case 1
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    Case 1: Kerley A, B and C lines (arrowed)
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    Case 2
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    Case 3
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    Kerley B lines
    Case 4: Kerley B lines
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    Case 5: CT equivalent
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