Compare the size of the vessels in regions of dark lung and regions of lighter lung.
What is the significance of the difference in vessel size?
Case 29
Section 1
Compare images 1 and 2 below.
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Compare the size of the vessels in regions of dark lung and regions of lighter lung. What is the significance of the difference in vessel size?
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What happens to the regions of dark and light lung on the expiratory image? What is the significance?
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Section 2
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Find a region of dark lung with small vessels in the right lung. Find 2 regions of lighter lung with larger vessels in the right lung. | ||||||
Image 2--End-expiration
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Central Pulmonary Arteries Note also that the central pulmonary arteries are at least twice the size of their accompanying bronchi, indicating central pulmonary artery enlargement.
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The dark regions of lung in mosaic perfusion typically affect one or more lobules, as in this case and in Case 28 (use the "back" button in the menu bar to return). Differences in perfusion (whether due to airway or vascular disease) result in dark areas of decreased alveolar blood flow and lighter areas of normal or increased alveolar blood flow.
Section 3: Mosaic Perfusion
Mosaic Perfusion in Vascular Disease
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Causes of Mosaic or Inhomogeneous Perfusion
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Note: The contrast between light and dark is not accentuated on the expiratory image. |
Note: The contrast between light and dark is accentuated on the expiratory image. |
Section 4
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Histologic Findings--Large Muscular Arteries Elastic and muscular arteries are involved. Here, a section of a muscular artery has been stained with the elastic van Gieson stain. The elastic layer on both sides of the media is black. Collagen and the muscular media stain red. The media is thickened and there is focal intimal fibrosis. The adventitia is fibrotic. Find the thickened arterial media. Find the fibrous intimal thickening. Find the adventitial fibrosis. |
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Small Muscular Arteries Smaller arteries often show concentric intimal thickening with marked narrowing of the lumen. In this H&E-stained section it is difficult to separate the intima, which is pale blue, from the media, which is pink. This vessel accompanies a respiratory bronchiole, indicating that it is a very small branch of the pulmonary artery. Outline the boundary between intimal and media. | ||||||
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Further damage to vessels is shown here. A narrowed parent artery is present to the left of center. Above it is a branch that shows a rounded collection of slit-like channels without any residual media. More distally are two, thin-walled, empty vascular channels that must be distinguished from alveoli. The airway lies to the left. Find the parent artery. Find the collection of slit-like channels without a media. What is it called? Find the 2 thin-walled vascular channels. What are they called? |
Differential diagnosis of mosaic perfusion of vascular disease on HRCT: Pre-capillary pulmonary hypertension (primary or secondary, including chronic embolic hypertension), pulmonary veno-occlusive disease
Histologic differential diagnosis: Plexogenic angiopathy can be idiopathic (primary) or associated with congenital heart defects (Eisenmenger's syndrome), schistosomiasis, HIV infection, collagen vascular diseases, cirrhosis of the liver, or intravenous drug abuse.
Diagnosis: Primary pulmonary hypertension: plexogenic pulmonary angiopathy
Diagnostic features of pulmonary hypertension on HRCT
See Case Study 6 for another example of plexogenic pulmonary angiopathy.
END
The size difference signifies mosaic perfusion, with smaller-sized vessels located in regions of darker lung.
The light lung becomes lighter and the dark lung becomes lighter. This pattern means that the mosaic perfusion is caused by primary abnormalities in the vessels rather than being secondary to air-trapping (compare with Case 28).
Lighter lung with larger vessels
Adventitial fibrosis (contributes to size of arteries on HRCT)
Slit-like channels without a media. This is a plexiform lesion, which develops after inflammatory destruction of the arterial wall at a branch point.
Thin-walled vascular channel. These channels are called dilation lesions. They occur distal to the stenosing plexiform lesion.
