Chest Computed Tomography-Ground-Glass Infiltrates


Secondary Pulmonary Lobule (see Pulmonary Anatomy)

The Secondary Pulmonary Lobule is a Functional Unit of the Lung Surrounded by an Interlobular Septum (W.S. Miller [The lung. 2nd ed. Springfield, IL: Charles C Thomas, 1947]) (NEJM, 2020) [MEDLINE]

  • The Lobular Bronchiole and a Pulmonary Artery Branch Supply Multiple Acini within a Pulmonary Lobule
  • Lymphatics and Pulmonary Veins are Located within the Interlobular Septum
  • Lymphatics Also Surround the Bronchovascular Sheath

Etiology of Ground-Glass Infiltrates on the Chest CT Scan

Ground-Glass Infiltrates Occur on the Chest CT Scan When Air within the Acini in the Pulmonary Lobule is Displaced by Any of the Following Four Mechanisms

  • Partial Alveolar Collapse (Atelectasis) (see Atelectasis)
    • Due to Obstruction, Compression, etc
  • Partial Alveolar Filling (Consolidation)
  • Interstitial Thickening
    • Due to Interstitial Lung Disease (ILD) (see Interstitial Lung Disease)
      • Thickened Interstitium
    • Due to Interstitial Pulmonary Edema (see Pulmonary Edema)
      • Lymphatic Engorgement by Fluid
    • Due to Lymphangitic Spread of Cancer (see Lung Cancer)
      • Lymphatic Engorgement by Tumor Cells
  • Increased Pulmonary Capillary Blood Flow


  • Miller WS. The lung. 2nd ed. Springfield, IL: Charles C Thomas, 1947
  • Case 25-2020: A 47-Year-Old Woman with a Lung Mass. N Engl J Med. 2020 Aug 13;383(7):665-674. doi: 10.1056/NEJMcpc2004977 [MEDLINE]