Primary Tuberculosis - Diagnosis

Since bacteriological diagnostics of primary tuberculosis has objective difficulties, in local forms of primary tuberculosis, X-ray examination is of particular importance, the informativeness of which largely depends on the methodology and technology. Sometimes, in patients with clinical signs of the disease and a turn in sensitivity to tuberculin, no pathological changes are detected on survey X-rays in two projections and on longitudinal tomograms of the chest organs. Only a slight expansion of the shadow of the root of the lung, a decrease in its structure, an increase in the root pulmonary pattern are noted. In this case, tuberculosis intoxication is usually diagnosed, since convincing data on local damage to the lymph nodes cannot be found. During a control study after 6-12 months, microcalcifications can be found in the root of the lung. Such dynamics of the process indicate tuberculosis of the intrathoracic lymph nodes, which was not recognized during the initial examination. The diagnosis of "primary tuberculosis" is established retrospectively.

CT can be used to objectively assess the density of lymph nodes and detect even small changes in their size. It is possible to examine all groups of intrathoracic lymph nodes, including bifurcation, retrocaval, and paraaortic, which are not visible on conventional radiography, and also to distinguish calcified arterial ligament from calcification in an intrathoracic lymph node.

In severe cases of tuberculosis of the intrathoracic lymph nodes, adenopathy can be detected by routine X-ray examination. On the X-ray in direct projection, inflammation of the nodes of the bronchopulmonary and tracheobronchial groups in the early phase is manifested by an increase in the shadow of the root of the lung in length and width. The outer border of the root becomes convex and blurred, its structure is disrupted, and it is impossible to distinguish the bronchial trunk. When the paratracheal lymph nodes are affected, an expansion of the median shadow with a semicircular or polycyclic edge is observed. With the resorption of perinodular inflammatory changes and dense consistency, the lymph nodes are visualized better and have clear contours. In such cases, the changes detected during X-ray examination are similar to the picture of a tumor lesion.

In the case of a favorable course of uncomplicated bronchoadenitis, the pattern of the lung root may become normal. However, more often the lung root is deformed due to fibrous changes. In some groups of lymph nodes, calcifications are formed over time, which are represented on radiographs by high-intensity inclusions with clear contours. CT allows us to trace how the impregnation of lymph nodes with calcium salts occurs. Large lymph nodes are usually calcified to a greater extent along the periphery, while calcifications in the form of granules are visible in the center. Smaller lymph nodes are characterized by point deposition of calcium salts in various sections.

In the radiological picture of the primary tuberculosis complex, three main stages are conventionally distinguished: pneumonic, resorption and compaction, petrification. These stages correspond to the clinical and morphological patterns of the course of primary tuberculosis.

In the pneumonic stage, a darkened area with a diameter of 2-3 cm or more, irregular in shape, with blurred contours and a heterogeneous structure is detected in the lung tissue. The central part of the darkening, caused by the primary lung lesion, has a higher intensity on the radiograph, and the surrounding perifocal infiltration is less intense. On the affected side, there is also an expansion and deformation of the shadow of the lung root with a blurred outer border. The darkening in the lung is associated with the shadow of the expanded root and sometimes completely merges with it, preventing a clear visualization of the root on the survey image. In the natural course of the process, the duration of the pneumonic stage is 4-6 months.

The stage of resorption and consolidation is characterized by gradual disappearance of perifocal infiltration in the lung tissue and perinodular infiltration in the area of the lung root. The components of the primary complex in the lung, lymph nodes and the lymphangitis connecting them can be determined more clearly. The pulmonary component is usually represented by a limited darkening or a focus of medium intensity, the lymph nodes - by expansion and deformation of the lung root. The "bipolarity symptom" of the lesion can be clearly identified. Subsequently, the size of the pulmonary component and the affected lung root continues to decrease; signs of calcification are gradually detected in them. The duration of the stage of resorption and consolidation is about 6 months.

The petrification stage is characterized by the formation of a highly intense focal shadow in the lung tissue with sharp contours (Ghon's focus) and high-density inclusions (calcifications) in the regional lymph nodes.

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