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 edema of the connective tissues of the interlobular septa. They usually occur when pulmonary capillary wedge pressure reaches 20-25 mmHg.

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.

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

Kerley lines are named after Sir Peter James Kerley (1900-1979), a British radiologist who in addition to describing the interstitial lines now known as Kerley lines, was a co-founder of the Faculty of Radiology (later to become the Royal College of Radiologists), and also attended to King George VI 3,4

Share article

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

Support Radiopaedia and see fewer ads

Cases and figures

  • Case 1
    Drag here to reorder.
  • Case 1: Kerley A, B and C lines (arrowed)
    Drag here to reorder.
  • Case 2
    Drag here to reorder.
  • Case 3
    Drag here to reorder.
  • Kerley B lines
    Case 4: Kerley B lines
    Drag here to reorder.
  • Case 5: CT equivalent
    Drag here to reorder.
  • Case 6: Kerley B lines
    Drag here to reorder.
  • Case 7: APO
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.