Kerley A-lines represent thickened septal plates between lung segments in patients with lymphangitic carcinomatosis: confirmation using 3D-CT lung segmentation analysis

Abstract

Purpose: Kerley A-lines are generally apparent in patients with pulmonary edema or lymphangitic carcinomatosis. There are two main thoughts regarding the etiology of Kerley A-lines, but no general agreement. Specifically, the lines are caused by thickened interlobular septa or dilated anastomotic lymphatics. Our purpose was to determine the anatomic structure represented as Kerley A-lines using 3D-CT lung segmentation analysis.

Materials and methods: We reviewed 139 charts of patients with lymphangitic carcinomatosis of the lung who had CT and X-ray exams with a maximum interval of 7 days. The presence of Kerley A-lines on X-ray was assessed by a radiologist. The A-lines on X-ray were defined as follows: dense; fine (< 1 mm thick); ≥ 2 cm in length, radiating from the hilum; no bifurcation; and not adjacent to the pleura. For cases with Kerley A-lines on X-ray, three radiologists agreed that the lines on CT corresponded with Kerley A-lines. The incidence of A-lines and the characteristics of the lines were investigated. The septal lines between lung segments were identified using a 3D-CT lung segmentation analysis workstation. The percentage of agreement between the A-lines on CT and lung segmental lines was assessed.

Results: On chest X-ray, 37 Kerley A-lines (right, 16; left, 21) were identified in the 22 cases (16%). Of these, 4 lungs with 12 lines were excluded from analysis due to technical reasons. Nineteen of the 25 lines (76%) corresponded to the septal lines on CT. Of these, 11 lines matched with automatically segmented lines (intersegmental septa, 4; intersubsegmental septa, 7) by the workstation. Two lines (8%) represented fissures. Four lines corresponded to the bronchial wall/artery (3 lines, 12%) or vein (1 line, 4%).

Conclusion: Kerley A-lines primarily represented thickened and continued interlobular septal lines that corresponded to the septa between lung segments and subsegments.

Keywords: Computed tomography; Interlobular septa; Kerley's A lines; Lung segmentation; Lymphatics.

Fig. 1

Study design and enrollment flow chart

Fig. 2

3D lung segmentation of a normal lung. The plate structure surrounding the lung segments of the upper lobes can be recognized as a linear shadow similar to the Kerley A-lines

Fig. 3

Case 6. Line 9. 88-year-old man with prostate cancer. Chest X-ray shows the Kerley A-line in the left lung. The line corresponds to the thickened septal line on CT and matched with the segmented lines between S3b and S3c by 3D segmentation analysis

Fig. 4

Case 5. Line 8. 35-year-old man with tongue cancer. Chest X-ray shows the Kerley A-line in the left lung. The line corresponds to the thickened septal line on CT and matched with the segmented lines between S3b and S3c by 3D segmentation analysis

Fig. 5

Case 3. Line 5. 51-year-old woman with gastric cancer. Chest X-ray shows the Kerley A-line in the left lung. The line corresponds to the thickened septal line on CT and matched with the segmented lines between S3b and S4 by 3D segmentation analysis

Fig. 6

Case 8. Line 11. 51-year-old woman with gastric cancer. Chest X-ray shows the Kerley A-line in the right lung. The line corresponds to the deformed right major fissure on CT. The right upper lobe is complete atelectasis

Fig. 7

Case 10. Line 16. 66-year-old woman with breast cancer. Chest X-ray shows the Kerley A-line in the right lung. The line corresponds to the bronchial wall (B1b) and artery (A1b) on CT