Tracheoesophageal fistula

Imaging Diagnostics of Fistula

Congenital fistula tracheoesophagea in adult patients requires a thorough instrumental examination. Computed tomography (CT) serves as the primary imaging modality of choice. When analyzing axial tomograms, the radiologist clearly visualizes a large defect—a pathological communication located between the posterior tracheal wall and the esophageal wall.

For the attending physician to thoroughly study the spatial anatomy of the fistula, routine slices are insufficient. Therefore, additional post-processing techniques are employed: oblique longitudinal reformation and 3D volume rendering. These provide comprehensive information regarding the dimensions and topography of the fistula.

Mechanisms of Bronchiectasis Development

Chronic processes in the airways are frequently accompanied by the development of bronchiectasis—permanent pathological dilation of the bronchi. Three key triggering factors are identified: lumen obstruction, direct bronchial wall injury, and parenchymal fibrosis.

In obstruction and direct wall injury, the formation of the so-called "vicious cycle" (vicious cycle) plays a leading role. It all begins with the formation of thick mucous plugs (mucus plugging) and the onset of bacterial colonization. Inflammatory cells actively release enzymes and specific cytokines, while multiplying bacteria produce toxins. This aggressive cocktail causes relentless, progressive destruction of airway tissues. As a result, mucus retention worsens, creating ideal conditions for further bacterial growth, thus closing the pathological loop.

A completely different mechanism is observed in parenchymal fibrosis. Here, dilation is secondary: the maturing fibrous tissue surrounding the airways begins to contract (undergoes retraction). It literally pulls the bronchial walls outward. Such bronchiectasis is referred to as traction bronchiectasis (traction bronchiectasis).

Pathomorphological Classification

As the pathological process worsens, the morphology of the dilated bronchi also changes. The classification includes three consecutive subtypes:

1. Cylindrical (cylindrical): the airway lumen expands relatively uniformly throughout its extent.
2. Varicose (varicose): the dilation becomes uneven, and the walls acquire a tortuous, somewhat serpiginous (serpiginous) contour.
3. Cystic (cystic): the most severe form.

Important note: as the extent of the process and the caliber of the dilated bronchi increase, secondary changes inevitably progress in the distal pulmonary parenchyma. These include phenomena of pulmonary tissue collapse (atelectasis) and pronounced local fibrosis.

Radiographic Findings

Classic chest radiography successfully detects airway pathology in the majority of clinical cases. The radiologist relies on several basic patterns:

• «Tram-track» sign (tramline opacities): thickened bronchial walls project as single thin lines or strictly parallel linear opacities.
• «End-on» appearance (end-on): when the X-ray beam passes along the axis of a thickened bronchus, it appears on the image as a cross-section — forming ring-shaped (ring) or curvilinear shadows.
• Infilling sign: when dilated lumens are filled with thick mucus or pus, they appear as dense tubular (tubular) or ovoid opacities of various sizes.
• Cystic changes: manifest as a cluster of multiple thin-walled ring-shaped shadows. A characteristic feature is the presence of horizontal air-fluid levels (air-fluid levels) within them.

Additionally, with concomitant obliterative bronchiolitis (obliterative bronchiolitis), plain chest radiography may reveal oligemia (depletion of the pulmonary pattern) in the basal zones, redistribution of blood flow to the upper regions, and moderate lung overinflation (overinflation), more often on the right side. Targeted views of the basal regions in such cases clearly demonstrate the aforementioned «tram tracks» and ring-shaped opacities reflecting bronchial dilation.

Class and exam questions

What else to study on this topic

• Technique of oblique longitudinal reformation and 3D reconstruction in the study of the trachea.
• The effect of bacterial toxins and cytokines on airway wall degradation.
• Mechanisms of atelectasis and fibrosis development in the distal pulmonary parenchyma.
• Oligemia and redistribution of pulmonary blood flow in obliterative bronchiolitis.
• Differential diagnosis of tubular and ovoid opacities on radiographs.

Other topics in the «Chest Radiology» section

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