Chest Computed Tomography-Ground-Glass Infiltrates



Background

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

Increased Pulmonary Capillary Blood Flow/Volume

  • Due to Congestive Heart Failure (CHF) (see Congestive Heart Failure) (Chest, 2004) [MEDLINE]
    • Despite the Increase in Pulmonary Capillary Blood Volume, DLCO is Typically Decreased in Congestive Heart Failure
      • This is Believed to Be Due to Thickening of the Alveolar-Capillary Barrier from the Accumulation of Fluid or Fibrosis, Resulting in Decreased Alveolar Capillary Membrane Conductance (Chest, 2004) [MEDLINE]
  • Due to Exercise (J Appl Physiol, 1960) [MEDLINE]
  • Due to Microgravity Environment

References