Patient Identifier: [Not specified] Examination Date: [Not specified] Modality: Chest X-ray (Posteroanterior & Anteroposterior views) / High-Resolution CT Chest (if applicable) Clinical Indication: Suspected pulmonary venous hypertension / interstitial edema. 1. Definition & Classification Kerley lines are linear opacities seen on chest imaging, representing thickened interlobular septa due to fluid, cellular infiltration, or fibrosis. They are classified as: