Intralobular septal thickening 2021-02-03T13:28:12Z Intralobular lines Intralobular septal thickening is a computed tomography finding of increased width of the walls (septa) within a pulmonary lobule. Secondary pulmonary lobules represent a cluster of up to 30 acini 9 supplied by a common distal pulmonary artery and bronchiole. These clustered acini are bounded by interstitial fibrous septa (interlobular septa) which outline an irregular polyhedron of varying size between 1 and 2.5 cm. Interlobular septal thickening is seen on chest radiographs as thin linear opacities at right angles to and in contact with the lateral pleural surfaces near the lung bases. In contrast, intralobular septal thickening are visible as fine linear opacities in a lobule when the intralobular interstitial tissue is abnormally thickened. When numerous, they may appear as a fine reticular pattern. Intralobular lines may be seen in various conditions, including interstitial fibrosis and alveolar proteinosis. Pulmonary interstitial thickening