Kerley lines

thin linear pulmonary opacities caused by fluid or cellular infiltration into the interstitium of the lungs. Kerley B lines are thickened interlobular septa visible as 12 mm linear opacities about 3060 mm long in the subpleural region. These are most readily identified at the costophrenic angles on the frontal radiograph (Fig.1) and substernal region on lateral radiographs. Kerley A lines are longer lines frequently coursing diagonally toward the hila in the inner half of the lungs. These are caused by distension of anastomotic channels between peripheral and central lymphatics of the lungs. Kerley B lines are usually indicative of interstitial pulmonary oedema and are observed much more frequently than Kerley A lines. Progression to alveolar oedema may obscure Kerley lines. Kerley lines can be caused by other processes such as pulmonary fibrosis, interstitial deposition of heavy metal particles, and malignant cells (lymphangitic metastasis). Chronic Kerley B lines may be caused by fibrosis and haemosiderin deposition caused by multiple previous episodes of pulmonary oedema.

CBH