Radiological picture of bronchitis

Bronchial Visualization and Lung Root Anatomy

To understand the pathological changes of the bronchial tree, it is necessary to know the radiological anatomy of the lung roots. Normally, the density (shadow) of the hila on conventional radiographs and computed tomography scans is caused primarily by the major blood vessels (pulmonary arteries and veins). The bronchial walls are very thin, so their contribution to the overall volume of the root is minimal, although they are easily differentiated from blood vessels.

On a posteroanterior chest radiograph, an important landmark is the hilar points (hilar points), which are the intersection points of the superior pulmonary vein and the descending lower lobe pulmonary artery. The left hilar point is usually located at the same level as the right or slightly higher.

In MRI diagnostics (using standard spin-echo sequences), normal bronchi and vessels produce a relatively weak signal. This is explained by the absence of a signal from the air inside the bronchial lumen and from rapidly flowing blood. The only sources of signal in this zone are the bronchial walls themselves, adipose tissue, lymph nodes, and slowly flowing blood.

Bronchial Obstruction and Lung Volume Loss

Obstruction of the lumen of a main or lobar bronchus (e.g., by an endobronchial tumor component or thick secretions) leads to the development of atelectasis (collapse) of the lung. Direct and indirect signs of such volume loss are distinguished on radiographs.

Direct Signs of Volume Loss:

• Displacement of fissures (displacement of fissures): the most reliable sign. The direction of displacement depends directly on which lobe has collapsed.
• Crowding of bronchi and vessels: an early sign resulting from the compaction of the pulmonary pattern against the background of a loss of aeration.
• Elevation of the hilum: occurs during upper lobe collapse.
• Small hilum (small hilum): observed during lower lobe collapse, when the collapsed tissue obscures the lower lobe pulmonary artery, and the interlobar artery rotates.
• Change in bronchial orientation: in upper lobe lesions, the ipsilateral main bronchus assumes a more horizontal position, whereas in lower lobe lesions, both main bronchi assume a vertical orientation.

Indirect signs include compensatory hyperinflation of adjacent healthy lobes. With pronounced collapse (e.g., of an entire lung), the contralateral lung may overexpand and cross the midline, forming a so-called mediastinal hernia.

CT Appearance of Bronchial Dilation (Bronchiectasis)

The most informative method for detecting structural deformations of the bronchi is high-resolution computed tomography (HRCT / HRCT). The main manifestation of chronic destructive processes is bronchial dilation, often accompanied by thickening of their walls.

Key CT Signs of Dilation:

1. Absence of bronchial lumen tapering toward the lung periphery (lack of tapering).
2. Signet ring sign (signet ring sign): on a cross-section, the diameter of the bronchial lumen is noticeably larger than the diameter of the accompanying branch of the pulmonary artery.
3. Appearance of visible bronchial lumens within 1 cm of the costal or mediastinal pleura (normally, they are not visualized there).

Several morphological types are distinguished:

• Varicose bronchiectasis (varicose bronchiectasis): the lumen acquires an uneven, beaded shape.
• Cystic bronchiectasis (cystic bronchiectasis): on longitudinal sections, they look like a "string of cysts," and on cross-sections, like a "cluster of cysts" (especially common in collapsed lobes). Air-fluid levels (air-fluid levels) may be visualized in the dependent parts of such dilated bronchi, indicating secretion retention.

Secretion Retention and Associated Changes

If dilated bronchi are filled with thick mucus, their lumen is not defined as air-filled on CT. Instead, the accumulated secretions (secretion accumulation) form dense lobulated V- or Y-shaped structures known as the "glove-finger" sign (glove-finger densities). If such a filled bronchus is scanned strictly perpendicularly, it will appear as a dense nodule.

In generalized forms (e.g., in cystic fibrosis / cystic fibrosis), multiple thin-walled ring-like shadows against a background of generalized lung overexpansion (hyperinflation) are frequently visible on imaging. In localized post-infectious forms, cylindrical bronchial dilations, mucoid impaction, and local atelectasis are more common. Atelectasis may be minimal, and its presence will be indicated only by vascular crowding, blurring of the diaphragmatic dome, and interlobar fissure displacement.

Class and exam questions

What else to study on this topic

• Radiological Topography of Major Pulmonary Vessels
• Mechanisms of Formation and Signs of Mediastinal Hernia
• Differential Diagnosis of Cystic Bronchiectasis
• Features of Lymphangitic Carcinomatosis on HRCT
• Radiological Patterns of Endobronchial Metastases

Other topics in the «Chest Radiology» section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.