Darkening of the pulmonary field or part of it

Most lung diseases are accompanied by compaction of the lung tissue, i.e. Decrease or absence of its airiness. Sealed cloth absorbs X-rays more strongly. Against the background of a light pulmonary field, a shadow appears or, as is customary, a blackout. The position, size and shape of the darkening depend, naturally, on the amount of damage. There are several types of darkening options. If the pathological process has captured all of the lungs, then on the roentgenogram the entire pulmonary field is darkened to some extent. This syndrome is denoted by the term "extensive darkening of the pulmonary field". It is not difficult to detect it - it catches your eye when you first look at the picture. However, you must immediately determine its substrate. Darkening of the entire pulmonary field is most often caused by obstruction of the main bronchus and atelectasis of the corresponding lung.

Atelectasized lung is airless, therefore its shadow is uniform. In addition, it is reduced, so the organs of the mediastinum are shifted towards the dimming. These two signs are enough to recognize atelectasis of the lung and to accurately determine its origin (tomography of the main bronchus, its damage, foreign body) with the help of tomography and fibrobronchoscopy. A similar pattern can be obtained after removal of the lung (pneumonectomy), but this option is clear from an anamnesis.

Another pathological process, in which the organs of the mediastinum are shifted towards extensive dimming, is fibrotorax with cirrhosis of the lung. However, with this pathology, darkening is never homogeneous: on its background, the areas of preserved pulmonary tissue, inflated lobules, sometimes cavities, coarse fibrous cords, etc., are distinguishable.

Inflammatory infiltration very rarely extends to the entire lung. If this still happened, then there is also a vast darkening of the pulmonary field. It is distinguished from atelectasis not only in the clinical picture, but also in radiologic symptoms. The mediastinum organs remain in place with pneumonia, and on the background of the dimming, it is possible to catch the lumens of bronchi filled with air.

Finally, it is very important to point out that the darkening of the pulmonary field may be due not only to the compaction of the lung tissue, but also to the fluid accumulated in the pleural cavity. With great efflorescence, the obscuration becomes extensive and uniform, as in atelectasis, but the mediastinum organs are displaced in the opposite direction.

Much more often the pathological process affects not all the lungs, but only a share, part of a share, a segment or even a subsegment. On the X-ray patterns, a shadow is detected, according to position, size and shape, coinciding with the altered lobe, segment or subsegment. This syndrome was called "limited darkening of the pulmonary field." Its substrate is the infiltration of the lung tissue (the accumulation of any exudate in the alveoli), atelectasis or sclerosis of the lung tissue, tumor proliferation.

Having found a limited obscuration on radiographs, it is first of all necessary to establish its topography, i.e. Determine which fraction, segment or subsegment is compacted. The task is essentially simple if there are pictures in two projections, since each segment and each segment occupy a certain place in the chest cavity. It is more difficult to install a darkening substrate. Of course, the history data, the results of clinical and laboratory studies often shed light on the nature of the compaction of lung tissue. However, given the clinical information, the radiologist always makes up his own opinion, guided by a number of considerations. They are convenient to list on the example of the defeat of the upper lobe of the right lung.

In case of pneumonic infiltration, the dimming in size corresponds to the proportion, has a distinct straight or convex bottom, separating it from the middle lobe (the interlobar pleura). On the background of blackout, bronchial lumens can be seen. The position of the mediastinum is not changed. With atelectasis, the proportion is reduced, the lower border is retracted, the shadow is uniform, and the mediastinum is slightly shifted toward the dimming. In case of pneumosclerosis, the proportion is also reduced, and the mediastinum is stretched toward it, but the shading is non-uniform: it shows blemishes corresponding to the swollen areas of the preserved pulmonary tissue or cavities, as well as interlacing dark strips of fibrous tissue. Unlike atelectasis, the patency of the bronchi is preserved, which is perfectly displayed on the tomograms.

The above considerations on differential diagnostics fully refer to the intra-lobe segmental pathological processes. However, the smaller the amount of damage, the more difficult it is to unravel its nature. The most general considerations are as follows. Pneumonic and tuberculous infiltration has the appearance of diffuse or focal blackouts with blurred outlines (for more details, see below). A more or less delimited shadow with irregular contours indicates a tumor growth. There are no bronchial lumens in it, enlarged lymph nodes in the root of the lung can be seen. Seal caused by a major lung infarction, gives a triangular shadow, the base adjacent to the chest wall or the inter-lobe border. Of course, such facts as the presence of an obvious source of thromboembolism (for example, thrombophlebitis of the lower extremity), chest pain, dyspnea, hemoptysis, overload of the right heart, detected by electrocardiography and, of course, help diagnose the infarction.

The darkening of a part of the pulmonary field is not necessarily associated with compaction of the lung tissue: a tumor growing from the rib or pleura, pleural cleavage and pleural effusion will also cause a darkening of the pulmonary field, since they too absorb a large amount of X-ray radiation. However, using X-rays in different projections and especially computer tomograms, it is always possible to establish the marginal localization of the lesion, outside the pulmonary tissue.

Limited darkening of part of the pulmonary field may be due to diaphragmatic hernia, i.e. The exit of the abdominal cavity organs into the thoracic cavity through a defect in the diaphragm. In this case, the darkening is inseparable from the contour of the diaphragm, sharply delimited from the lung tissue. If the part of the hernia contains part of the stomach or intestinal loops, then the shading is non-uniform due to the presence of bleachings caused by accumulations of gas in these organs. All doubts eliminate the research conducted after taking the patient's barium suspension, which consistently fills the stomach and intestines. In this case, the picture shows which part of the digestive canal is in the hernia, and it is possible to establish the localization of the hernial gates.

In the special syndrome of round shadow in the pulmonary field, limited darkening of the pulmonary field is distinguished, in which the shadow of pathological formation in the images in all projections has the form of a circle, semicircle or oval with a diameter of more than 1 cm. Such a shadow determines the focus of the lesion of the spherical or ovoid form. Substrate may be eosinophilic infiltrate, tuberculous infiltrate or tuberculoma, rounded area of pneumonic infiltration, lung infarction, closed cyst (bronchial, retentional, echinococcal, alveococcal), aneurysm, benign tumor, malignant tumor (primary or metastatic) and many other pathological conditions.

Differential diagnosis of single and multiple round shadows in the lungs is sometimes difficult. In these cases an important role is played by the history and clinical picture of the disease (for example, pneumonia, lung infarction, metastatic tumors). In addition, a great help is provided by the fact that many diseases, in which circular shadows are visible on the roentgenogram, are rare. "What is often, often, and what is rare, it is rare," old radiologists like to repeat. Practically we have to distinguish mainly closed cysts, tuberculomas and lung tumors.

The closed cyst is defined as a round or ovoid shadow, sharply delimited from the surrounding lung tissue. With CT, the cyst immediately gives itself up, because, according to the densitometry, the contents of it are liquid.

Differentiation of tuberculoma, benign tumor and cancer can be facilitated if there are radiographs performed earlier, since the rate of growth of education can be established. Otherwise, there may be a need for transthoracic puncture biopsy, since the X-ray picture in these pathological conditions can be very similar. However, there are reliable reference points for X-ray differential diagnosis. Of benign tumors of the lung, the most common is a hamartoma. She, as well as tuberculoma and cancer, gives on the roentgenogram a rounded shadow with sharp and not exactly smooth outlines, but it is easy to recognize if there are calcareous or bony inclusions in the depth of the node. Signs of tuberculoma can to some extent be considered tubercular foci around it or in other parts of the lungs, as well as the presence of a sulcus cavity in the place where the tuberculoma includes the draining bronchus. Primary lung cancer is evidenced by rapid growth, the appearance of narrow lymphangitis strips to the periphery of the node and in the direction of the lung root, an increase in lymph nodes in the root. When a single globular formation is found in the lung, it is recommended to use the following diagnostic program.

A peculiar form of blackout is the ring-shaped shadow in the pulmonary field - an x-ray image of the cavity containing gas or gas and liquid. An obligatory requirement for isolating such a syndrome is the closure of the ring on X-ray grams in different projections. The fact is that in a picture in any one projection the intersecting shadows of the vessels may resemble a ring. Sometimes ring-shaped figures in a picture in one projection can be formed by bone bridges between the ribs.

The cavity of the abscess contains gas and liquid; in it the characteristic horizontal level of a liquid is visible. The walls of the abscess are thick, and in the surrounding pulmonary tissue there is an infiltration zone with blurred outlines. The fresh tubercular cavern has the appearance of an annular shade around which tubercular foci are scattered or the belt of densified lung tissue is located. The inner contour of the cavity is at first uneven, bay-like, then it becomes smooth. Dimensions of the cavity range from a few millimeters to several centimeters. Peripheral lung cancer does not rarely give a symptom of the cavity. As a result of the disintegration of necrotized tumor tissue, one or more cavities with scalloped edges appear in it. As the necrotic masses are torn away, the cavity can become rounded with even outlines, but always at least in a limited area remains a tuberous mass on the wall of the cavity. The outer contours of the cavity are uneven and relatively sharply delimited from the surrounding lung tissue.

The most common type of blackout is focal shadows. This term denotes rounded or irregularly shaped shadow formations, the sizes of which vary from 0.5 mm to 1 cm. It is conventionally considered to be foci up to 2 mm miliary, from 2 to 4 mm in small, from 4 to 8 mm medium and from 8 to 12 mm large. We only note that a single circular focus larger than 1 cm is usually referred to as a round shadow syndrome in the pulmonary field.

The number of focal shadows may be different. In some cases this is a single entity, in others it is a group of nearby foci. Sometimes there are many foci. If they cover a fairly large area, but not larger than the tip of the lung and the two adjacent intercostal spaces on a direct radiograph, talk about limited dissemination. More scattered foci are known as widespread dissemination. There are, finally, cases of diffuse dissemination, when the foci densely populate both lungs.

In the analysis of radiographs, it is first of all necessary to take into account the localization of the foci. Their location in the tops and outer areas of the subclavian zone in most cases indicates the tubercular nature of the disease - focal pulmonary tuberculosis. The presence of foci in the middle and lower parts of the lung is characteristic of focal pneumonia. With special care, it is necessary to analyze the contours and structure of the foci, as well as the pulmonary background around them. The irregular outlines of the foci are a sign of an active inflammatory process. This is also evidenced by the intensified pattern in the same zone and the tendency of foci to fuse. Dense clearly delineated foci - evidence of a granulomatous or ceased inflammatory lesion. Part of the tuberculosis foci in the inactive phase of the disease is calcified.

Usually, diagnosis and establishment of the nature of focal formations in the lungs with due attention to clinical data do not cause great difficulties. Difficulties arise mainly in diffuse dissemination. As a rule, the decision is made on the basis of the results of the analysis of the survey lung radiographs, but if there are clinical signs of tuberculosis activity or closely grouped foci, it is advisable to perform a tomography scan to identify cavities invisible in the survey images.

[1], [2], [3]