Intralobar septal oedema: 'D' lines.

A combined radiological and autopsy study of pulmonary oedema enables recognition of oedema lines other than Kerley 'A', 'B' and C lines. These have been designated 'D' lines. At least three varieties have been noted: (i) thick, long often angular lines seen mainly anteriorly overlying the heart shadow on the lateral film. These may also appear as horizontal or vertical band shadows, on the frontal view. (ii) Short and straight lines, occurring basally and often slightly thicker at the pleural surface, which on autopsy lung radiographs are associated with puckering of the pleura. They have also been recognised on lateral films where they resemble the pleural end of a fissure but have been seen in positions where fissures do not mormally occur, or in addition to the normal fissure. (iii) A subpleural reticular pattern surrounding spaces 1-2 cm in diameter. This has been noted only on autopsy-inflated lungs and not detected on in vivo chest radiographs. The long 'D' lines or D(i) lines occur in areas where 'B' lines are inconspicuous or absent and vice versa. Whereas 'B' lines are most prominent in areas of macroscopic alveolar pulmonary oedema, D(i) lines occur where macroscopic alveolar pulmonary oedema is often inconspicuous. The recognition that lines other than 'A', B and 'C' occur in case of pulmonary oedema greatly assists in the interpretation and diagnosis of the shadows on chest radiographs associated with pulmonary oedema.