Changes in the pulmonary and root pattern

Changes in the pulmonary pattern are a syndrome often observed in lung diseases. It is often combined with a disruption of the structure of the lung root. This is understandable: after all, the pulmonary pattern is formed primarily by arteries originating from the root, so many pathological processes affect both the lung parenchyma and its root.

Assessing the state of the pulmonary pattern is not an easy task even for a radiologist. This is explained by the existence of different types of branching of the pulmonary vessels, considerable age and individual differences. Nevertheless, it is possible to identify some general indicators of normal pulmonary and root pattern.

In a healthy person, the pattern is clearly visible in both lung fields. It consists of straight or arcuate branching stripes, circles and ovals. All these figures are shadow images of arteries and veins located in the lungs at different angles to the direction of the X-ray beam. The largest vessels are located in the root zone, the pattern here is richer, and its elements are larger. Towards the periphery, the caliber of the vessels decreases, and in the outer zone of the lung fields only very small vascular branches are visible. A normal pattern is characterized by regular branching, fan-shaped divergence of pattern elements from the root to the periphery, continuous decrease in the size of these elements from the root zone to the outer, sharpness of contours and the absence of cellularity.

It is advisable to begin the analysis of the drawing with an assessment of the image of the lung roots. The shadow of the left lung root is localized slightly above the shadow of the right root. In the image of each root, one can distinguish the shadows of the arteries and light stripes corresponding to large bronchi. In the case of pulmonary congestion and blood stagnation in them, the caliber of the vessels in the roots increases. With fibrosis of the cellular tissue in the hilum of the lung, the shadow of the root becomes poorly differentiated, and it is no longer possible to trace the outlines of individual anatomical elements in it. The outer contour of the root is uneven, sometimes convex towards the pulmonary field. With an increase in bronchopulmonary lymph nodes, rounded formations with external arcuate contours appear in the root.

Of the many variations of changes in the pulmonary pattern, two play a special role: its amplification and deformation. Amplification of the pulmonary pattern is an increase in the number of elements per unit area of the pulmonary field and the volume of the elements themselves. A classic example is congestive pulmonary congestion, often observed in mitral heart defects. The changes that occur in this case are bilateral and affect both pulmonary fields along their entire length. Enlarged vascular trunks are visible in the roots. The branches of the pulmonary artery are enlarged and can be traced to the periphery of the pulmonary fields. The correct branching of the vessels is not disturbed. Deformation of the pulmonary pattern is a change in the normal position of the elements of the pattern and their shape. In this case, the direction of the shadow of the vessels changes, in places these shadows have uneven outlines, expand towards the periphery (due to infiltration or fibrosis of the perivascular tissue). Such changes can be determined in a limited area and then are most often the result of an inflammatory process. However, pathological restructuring of the pattern can affect the lung fields over a significant area, which occurs in diffuse (disseminated) lung lesions.

Diffuse (disseminated) lung lesions include pathological conditions in which widespread changes are observed in both lungs in the form of scattered foci, an increase in the volume of interstitial tissue, or a combination of these processes.

Radiographically, diffuse lesions manifest as one of three syndromes:

1. focal (nodular) disseminated lesion;
2. reticular restructuring of the pulmonary pattern;
3. reticular-nodular (reticulonodular) lesion.

In disseminated focal lesions, radiographs show scattering of multiple foci in both lungs. The substrate of these foci is different - granulomas, hemorrhages, tumor tissue growths, fibrous nodules, etc. The reticular type of diffuse lesions is expressed in the appearance of new pattern elements on radiographs - a kind of cellularity, loopiness, resembling a multilayered web. The substrate of such a pattern is an increase in the volume of fluid or soft tissue in the interstitial space of the lungs. In the reticular-nodular type, the images show a combination of reticular reorganization and numerous focal shadows distributed over the pulmonary fields.

In perfusion lung scintigraphy, the main pathological syndrome is a defect in the distribution of the radiopharmaceutical. By analogy with X-ray data, extensive, limited, and focal defects can be distinguished. The absence of the radiopharmaceutical in the entire lung or an extensive defect in the lung image is most often observed in the central form of lung cancer. The nature of the segmental or lobar (lobar) defect can be different. It can be caused by impaired blood flow in the affected segment or lobe due to thromboembolism of the pulmonary artery branch. It occurs in atelectasis and in the area of the cancerous tumor. The accumulation of the radiopharmaceutical in the area of pneumonic infiltration and edema is significantly reduced. Subsegmental defects are often detected in obstructive bronchitis with severe emphysema and bronchial asthma during an exacerbation. Focal defects in the image are caused by the same processes as segmental ones, but they are also observed with pressure on the lung by pleural effusion and in areas of hypoventilation of the lung.

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