Differential diagnosis of pneumonia

Pulmonary tuberculosis

Regardless of the clinical variant of pneumonia and the form of pulmonary tuberculosis, when conducting differential diagnostics between these diseases, it is necessary, first of all, to use well-known methods for diagnosing pulmonary tuberculosis as a nosological unit.

Analysis of anamnesis data

The following anamnestic data allow us to assume that the patient has tuberculosis:

• the presence of tuberculosis in the patient's family;
• the patient has previously suffered from tuberculosis of any localization;
• clarification of the course of the disease. Acute onset and severe course are observed in acute miliary tuberculosis of the lungs and caseous pneumonia, in other forms of tuberculosis the onset of the disease is usually gradual, often completely unnoticeable. Acute lobar pneumonia has an acute onset, focal pneumonia begins gradually, but the duration of the initial period, of course, is significantly less than in tuberculosis of the lungs;
• information about previous illnesses. Such illnesses as exudative pleurisy, frequently recurring fibrinous (dry) pleurisy, prolonged subfebrile temperature of unknown genesis and unexplained malaise, sweating, weight loss, prolonged cough (especially if the patient does not smoke) with hemoptysis may be manifestations of pulmonary tuberculosis.

Analysis of external examination data of patients

Previous tuberculosis may be indicated by retracted, irregularly shaped scars in the area of previously affected cervical lymph nodes, and previous tuberculosis of the spine may be indicated by kyphosis.

Rapidly developing severe intoxication and severe condition of the patient are more characteristic of lobar or total pneumonia and are not characteristic of tuberculosis, with the exception of acute miliary tuberculosis and caseous pneumonia.

Analysis of physical data obtained during the examination of the lungs

Unfortunately, there are no physical symptoms that are absolutely pathognomonic for pulmonary tuberculosis. Such data as changes in vocal fremitus, bronchophony, bronchial breathing, crepitation, wet and dry wheezing, pleural friction noise can be observed both in pulmonary tuberculosis and in non-specific lung diseases, including pneumonia.

However, the following physical findings characteristic of pulmonary tuberculosis may have some diagnostic value:

• localization of pathological percussion and auscultatory phenomena mainly in the upper parts of the lungs (of course, this is not an absolute rule);
• scarcity of physical data compared to X-ray data (an old doctors' aphorism: "little is heard, but much is seen in pulmonary tuberculosis and much is heard, but little is seen in non-tuberculous pneumonia"). Of course, this pattern does not apply to all forms of tuberculosis, but can be observed in focal, miliary tuberculosis, tuberculoma.

Setting up tuberculin tests

The administration of tuberculin tests (tuberculin diagnostics) is based on the determination of tuberculin allergy - increased sensitivity of the body to tuberculin, which occurs as a result of infection with virulent mycobacteria of tuberculosis or BCG vaccination.

The most commonly used intradermal Mantoux test involves injecting 0.1 ml of tuberculin into the skin of the inner surface of the middle third of the forearm. The test results are assessed after 72 hours by measuring the papule diameter using a transparent millimeter ruler. The transverse (relative to the arm axis) diameter of the papule is recorded; the reaction is considered negative if the papule diameter is from 0 to 1 mm, questionable if the diameter is 2-4 mm, positive if the diameter is 5 mm or more, hyperergic if the diameter is 17 mm or more in children and adolescents and 21 mm or more in adults. Vesicular-necrotic reactions are also considered hyperergic, regardless of the size of the infiltrate.

A positive and especially hyperergic tuberculin test may indicate the presence of pulmonary tuberculosis. However, a final diagnosis of pulmonary tuberculosis is made only on the basis of a comprehensive clinical, laboratory and radiological examination of the patient, while, of course, taking into account the results of tuberculin tests.

Microbiological diagnostics of tuberculosis

The detection of Mycobacterium tuberculosis in sputum, bronchial washings, and pleural exudate is the most important method of diagnosing tuberculosis. Classical microbiological methods are used: bacterioscopy, culture or sowing, and biological testing on laboratory animals sensitive to tuberculosis infection.

Sputum analysis is one of the main and most common methods. To increase the sensitivity of the method, the flotation method is used, in which mycobacteria are extracted from an aqueous suspension of sputum using liquids with a relative density lower than that of water (xylene, toluene, gasoline, benzene). In this case, the frequency of detection of mycobacteria increases by at least 10% compared to conventional microscopy.

Smears are prepared from native sputum. Staining is performed using the Ziehl-Neelson method. Mycobacteria are detected in the preparation as thin, straight or slightly curved, bright red rods.

In recent years, the method of luminescent microscopy has been used. The method is based on the ability of mycobacteria lipids to perceive luminescent dyes and then glow when irradiated with ultraviolet rays. Mycobacterium tuberculosis gives a bright red or luminescent yellow glow on a green background (depending on the type of dye) when examined with luminescent microscopy. Luminescent microscopy significantly increases the effectiveness of the bacterioscopic method for detecting mycobacterium tuberculosis.

The seeding method (cultural method of detecting Mycobacterium tuberculosis) is more sensitive than bacterioscopic. It detects Mycobacterium tuberculosis in sputum if there are several dozen viable individuals in 1 liter of it. Various nutrient media are used to cultivate Mycobacterium tuberculosis. WHO experts recommend the Lowenstein-Jensen medium (a dense egg medium) as a standard medium for the primary isolation of the pathogen, on which good growth of Mycobacterium tuberculosis is obtained on the 15-25th day after seeding the bacterioscopically positive material.

When bacterioscopically negative material (sputum) is sown on dense nutrient media, the average duration of mycobacteria growth is 20-46 days, however, individual strains can grow up to 60-90 days. That is why sputum cultures should be kept in a thermostat for at least 3 months. Then, a smear from the grown colonies, stained according to Ziehl-Neelsen, is examined microscopically. Mycobacterium tuberculosis is detected as bright red or dark red rods.

A biological test is the most sensitive method for detecting Mycobacterium tuberculosis. It is used when the results of bacterioscopy and sputum culture are negative, but there is still a suspicion of tuberculosis. The test involves introducing specially processed sputum of the patient into a guinea pig. The pig is then slaughtered after 3 months and, if the biological test is positive, morphological signs of tuberculosis are found in the organs and tissues. During an autopsy, smears are taken from the organs for bacterioscopic examination. If there are no macroscopic signs of tuberculosis in the organs, a culture is made from the lymph nodes, spleen, liver, lungs and specially processed material on dense nutrient media.

Due to its labor intensity, the biological method is used relatively rarely.

X-ray examination of the lungs

In the diagnosis of pulmonary tuberculosis, the leading role belongs to X-ray examination methods. L. I. Dmitrieva (1996) suggests using them as follows:

• mandatory radiological diagnostic minimum (large-frame fluorography, survey radiography);
• in-depth radiological examination (radiography in two mutually perpendicular projections; fluoroscopy; standard tomography);
• additional X-ray examination (various methods of X-ray and tomography, including computed tomography and magnetic resonance imaging).

Characteristic radiological manifestations of individual forms of pulmonary tuberculosis are presented below.

Focal pulmonary tuberculosis

Focal pulmonary tuberculosis is a clinical form characterized by a limited inflammatory process (size of foci about 10 mm) and a low-symptom clinical course. The main clinical features of focal pulmonary tuberculosis are as follows:

• a long-term chronic wave-like course with alternating phases of exacerbation and attenuation. Such a course is not typical for acute pneumonia;
• absence of obvious clinical manifestations even in the acute phase, and even more so in the consolidation phase; with pneumonia, as a rule, the symptom of intoxication is expressed significantly, especially with lobar pneumonia;
• characterized by prolonged coughing without secretion or with secretion of a small amount of sputum (even if the patient is not a smoker);
• listening to fine bubbling rales in a limited area of the lung and, as a rule, after coughing;
• characteristic radiographic picture.

Radiological manifestations of focal pulmonary tuberculosis can be divided into three main groups):

• fresh forms are distinguished by poorly defined lesions of various shapes and sizes, sometimes merging against the background of pronounced lymphangitis;
• subacute forms are characterized by more sharply defined foci due to pronounced productive changes;
• fibrous-indurative changes with a predominance of linear strands over focal shadows.

During an exacerbation of focal tuberculosis, a zone of perifocal inflammation appears around old foci and new foci may develop against the background of dense old foci.

Infiltrative pulmonary tuberculosis

Infiltrative pulmonary tuberculosis is a clinical form characterized by a predominantly exudative type of inflammatory process with a tendency to rapid formation of caseous necrosis and destruction.

In terms of size, tuberculous infiltrates can be small (from 1.5 to 3 cm in diameter), medium (from 3 to 5 cm) and large (more than 5 cm).

Clinical symptoms of infiltrative pulmonary tuberculosis are determined by the size of the lesion and the phase of the process.

The following clinical and radiological variants of infiltrative pulmonary tuberculosis are distinguished:

• cloud-like variant - characterized by a gentle, non-intensive homogeneous shadow with unclear contours. In this case, rapid formation of decay and a fresh cavity is possible;
• round variant - manifested by a rounded, homogeneous, low-intensity shadow with clear contours, the diameter of the shadow is more than 10 mm;
• lobit - the infiltrative process affects the entire lobe, the shadow is inhomogeneous with the presence of decay cavities;
• periscissuritis - an extensive infiltrate localized in the interlobar fissures and often causing the development of interlobar pleurisy, while the shadow on one side has a clear outline, on the other - its contours are blurred;
• lobular variant - characterized by a non-homogeneous shadow formed as a result of the fusion of large and small foci.

It is very difficult to differentiate infiltrative pulmonary tuberculosis and acute pneumonia by clinical signs, since there is a great similarity in the clinical manifestations of both these diseases. As a rule, infiltrative tuberculosis, like acute pneumonia, occurs with high body temperature, pronounced symptoms of intoxication, and physical data are also similar. However, unlike pneumonia, hemoptysis is much more common in infiltrative tuberculosis. Very rarely, tuberculous infiltrate is asymptomatic or has few symptoms. In diagnosing infiltrative pulmonary tuberculosis, the leading role is played by X-ray examination of the lungs, a sharply positive tuberculin test, detection of mycobacteria in sputum, and a clear positive effect of anti-tuberculosis therapy.

In addition, it should be taken into account that all clinical and radiological variants of infiltrative tuberculosis are characterized not only by the presence of an infiltrative shadow, but also by bronchogenic seeding in the form of fresh foci both in the lung in which there is an infiltrate and in the second lung. Quite often, with a tuberculous infiltrate, there is a "path" going from the infiltrate to the root of the lung, caused by inflammatory peribronchial and perivascular changes (this is clearly visible on radiographs). Finally, it should be taken into account that, despite the fact that a tuberculous infiltrate can be located in any part of the lung, it is most often localized in the region of the second bronchopulmonary segment and on the anterior radiograph is most often detected in the lateral zone of the subclavian region.

Caseous pneumonia

Caseous pneumonia is a clinical form of pulmonary tuberculosis, characterized by pronounced exudative inflammation of the entire lobe of the lung or most of it, which quickly gives way to caseous-necrotic changes ("cheesy" decay) with subsequent formation of cavities. The course of caseous pneumonia is severe.

Miliary pulmonary tuberculosis

Miliary pulmonary tuberculosis is a dissemination of the tuberculous process with the formation of small foci (1-2 mm) with a predominantly productive reaction, although caseous-necrotic changes are also possible. The disease begins acutely, the body temperature rises to 39-40 ° C, the intoxication syndrome is expressed sharply, patients are bothered by pronounced weakness, sweating (exhausting night sweats are possible), anorexia, weight loss, dyspnea, persistent dry cough. There are no significant changes in the percussion sound during percussion of the lungs, a small amount of dry wheezing can be heard during auscultation of the lungs due to the development of bronchiolitis. Thus, there is a certain similarity in the clinical manifestations of severe pneumonia and miliary pulmonary tuberculosis.

Disseminated pulmonary tuberculosis

Disseminated pulmonary tuberculosis is a clinical form characterized by the formation of multiple tuberculous foci. According to the course, acute, subacute and chronic forms of disseminated pulmonary tuberculosis are distinguished. Acute and subacute forms are characterized by a severe course, patients have high body temperature, chills, night sweats, a very pronounced intoxication syndrome, a cough is bothersome, usually dry, less often - with sputum production. Severe dyspnea may develop. When auscultating the lungs, one can hear fine bubbling rales, crepitation in the upper and middle sections. The main diagnostic method is radiological.

In acute disseminated tuberculosis, focal shadows are determined in the lungs, evenly distributed from the apices to the diaphragm - a picture of dense dissemination of small and medium-sized soft foci.

Subacute disseminated tuberculosis is characterized by the appearance of larger soft foci that merge with each other. The foci tend to decay and rapidly form cavities.

Chronic disseminated pulmonary tuberculosis usually develops unnoticed, its clinical course is long, periodic disseminations of the process in the lungs may not give a clear clinical picture or proceed under the guise of pneumonia, exacerbation of chronic bronchitis. Fibrinous or exudative pleurisy often develops. Physical data in chronic disseminated pulmonary tuberculosis are scanty: a shortening of the percussion sound can be detected, mainly in the upper parts of the lungs, under the areas of dullness, hard vesicular breathing can be heard, sometimes fine-bubble or isolated dry wheezing (due to bronchial damage). Chronic disseminated pulmonary tuberculosis, both acute and subacute, can be complicated by decay and cavity formation. In this case, a tetrad of symptoms is characteristic: cough with sputum production, hemoptysis, moist rales, and mycobacterium tuberculosis in sputum.

The progression of the process in chronic disseminated pulmonary tuberculosis leads to increased development of fibrosis and cirrhosis of the lungs.

Thus, disseminated pulmonary tuberculosis is quite difficult to distinguish from pneumonia. The decisive role in diagnostics belongs to the X-ray method of examination.

The main radiological signs of disseminated pulmonary tuberculosis are (M. N. Lomako, 1978):

• bilaterality of the lesion;
• polymorphism of focal shadows;
• alternation of clearly defined lesions with fresh, poorly defined lesions;
• localization of foci in the upper posterior costal regions (1-2 segments);
• different sizes of lesions in different parts of the lungs: in the upper parts the lesions are larger, with clear contours and even the presence of calcareous inclusions; in the lower parts the lesions are smaller in size with more blurred contours;
• symmetrical location of foci in both lungs in acute, asymmetrical - in chronic disseminated pulmonary tuberculosis;
• the appearance of decay cavities as the process progresses;
• progressive development of fibrosis and cirrhosis.

Differential diagnostics of pneumonia, pulmonary tuberculoma, cavernous and fibro-cavernous pulmonary tuberculosis is not difficult due to the fact that the named forms of tuberculosis have clear radiological manifestations.

Tuberculoma is an isolated, caseous-necrotic lesion encapsulated by connective tissue, round in shape, more than 1 cm in diameter.

In radiographic imaging, a tuberculoma looks like a clearly defined formation of a homogeneous or heterogeneous structure against the background of an intact lung. It is localized mainly in segments 1-2, 6. Its shape is round, the edges are smooth. Mostly, a tuberculoma has a homogeneous structure. However, in some cases, its structure is heterogeneous, which is due to calcifications, foci of enlightenment, fibrous changes.

The most important differential diagnostic sign, not typical for pneumonia, is the presence of a double path in tuberculoma, which goes from the tuberculoma to the root of the lung. This path is caused by dense peribronchial and perivascular infiltration. A capsule is often found around the tuberculoma. Focal shadows can be found in the lung tissue around the tuberculoma. During an exacerbation of the tuberculosis process, the X-ray image of the tuberculoma is less clear than in the remission phase, even a focus of decay can be outlined. With a progressive course of tuberculoma, with the development of communication between it and the draining bronchus, mycobacteria tuberculosis may appear in the sputum.

Tuberculoma is sometimes difficult to distinguish from peripheral lung cancer. The most reliable method for diagnosing tuberculoma is bronchoscopy with biopsy followed by cytological and bacteriological examination.

Exudative pleurisy

The need for differential diagnostics of pneumonia with exudative pleurisy is due to a certain similarity in the symptoms of both diseases - the presence of shortness of breath, symptoms of intoxication, increased body temperature, dull percussion sound on the affected side. The main distinguishing features are the following:

• a significantly more pronounced lag in breathing in the corresponding half of the chest in exudative pleurisy than in pneumonia;
• greater intensity of dullness on percussion in exudative pleurisy than in lobar pneumonia. Dullness of percussion sound in exudative pleurisy is considered absolute ("femoral"), it increases significantly downwards, and the finger-pleximeter feels resistance on percussion. In pneumonia, the intensity of percussion sound is lower;
• absence of auscultatory phenomena over the dullness zone (absence of vesicular and bronchial breathing, vocal fremitus, bronchophony);
• intense dense homogeneous darkening with an upper oblique border during X-ray examination of the lungs, displacement of the mediastinum to the healthy side;
• detection of fluid in the pleural cavity using ultrasound and pleural puncture.

Pulmonary infarction

Pulmonary infarction occurs as a result of pulmonary embolism. The main signs that distinguish it from pneumonia are:

• the appearance at the beginning of the disease of intense pain in the chest and shortness of breath, then - an increase in body temperature; with lobar pneumonia, the relationship between pain and an increase in body temperature is inverse: as a rule, a sudden increase in body temperature and chills are observed; after this, pain in the chest appears, sometimes with pneumonia, a simultaneous increase in body temperature and chest pain are possible;
• absence of severe intoxication at the onset of pulmonary embolism;
• hemoptysis is a common symptom of pulmonary infarction, however, it can also be observed with pneumonia, but with pulmonary infarction, almost pure scarlet blood is released, and with pneumonia, mucopurulent sputum mixed with blood (or “rusty sputum”) is coughed up;
• a smaller area of lung damage (usually less than the size of a lobe), in contrast, for example, to lobar damage in pneumococcal pneumonia;
• a sharp decrease in the accumulation of the isotope in the infarction zone (due to a sharp disruption of capillary blood flow) during radioisotope scanning of the lungs;
• characteristic ECG changes that suddenly appear - deviation of the electrical axis of the heart to the right, overload of the right atrium (high pointed P wave in II and III standard leads, in lead aVF), rotation of the heart around the longitudinal axis clockwise with the right ventricle forward (appearance of a deep 5 wave in all chest leads). The above ECG changes can also be observed in acute lobar pneumonia, but they are much less pronounced and are observed less frequently;
• the presence of thrombophlebitis of the veins of the lower extremities;
• characteristic radiological changes - bulging of the cone a.pulmonalis, the darkening area has the shape of a strip, less often - a triangle with the apex directed towards the root of the lung.

Lung cancer

Lung cancer is a common disease. From 1985 to 2000, the number of patients with lung cancer will increase by 44%, and mortality by 34.4%. The following methods are used to diagnose lung cancer.

Analysis of anamnesis data

Lung cancer is more common in men, especially those over 50 years of age. As a rule, they have been abusing smoking for a long time. Many patients have occupational hazards that contribute to the development of lung cancer: working with carcinogenic chemicals, nickel, cobalt, chromium compounds, iron oxides, sulfur compounds, radioactive substances, asbestos, radon, etc. Of great importance in the diagnosis of lung cancer are the appearance of such symptoms as persistent cough, change in the timbre of the voice, the appearance of blood in the sputum, increased body temperature, loss of appetite, weight loss, chest pain. The importance of these anamnestic data increases even more if they are combined with deformation or blurring of the root of the lungs, first detected during an X-ray examination.

X-ray examination of the lungs

Peripheral lung cancer develops from the epithelium of small bronchi or from the epithelium of the alveoli and can be located in any area (segment) of the lung. However, it is most often localized in the anterior segments of the upper lobes of the lungs.

Radiographic manifestations of peripheral cancer largely depend on the size of the tumor. Radiographic signs of peripheral lung cancer can be characterized as follows:

• a small tumor (up to 1-2 cm in diameter) usually manifests itself as a darkening center of irregular round, polygonal shape; cancer of medium and large sizes has a more regular spherical shape;
• the intensity of the shadow of a cancerous tumor depends on its size. With a node diameter of up to 2 cm, the shadow has a low intensity, with a larger tumor diameter, its intensity increases significantly;
• very often the tumor shadow has a non-homogeneous character, which is caused by the uneven growth of the tumor, the presence of several tumor nodules in it. This is especially noticeable in large tumors;
• the contours of the tumor darkening depend on the phase of tumor development. A tumor up to 2 cm in size has an irregular polygonal shape and unclear contours. When the tumor is up to 2.5-3 cm in size, the darkening has a spherical shape, the contours become radiant. When the tumor is 3-3.5 cm in diameter, the contours of the tumor become clearer, however, with further growth of peripheral cancer, the clarity of the contours disappears, the tuberculosis of the tumor is clearly visible, sometimes cavities of decay are determined in it;
• a characteristic feature is Rigler's symptom - the presence of a notch along the contour of the tumor, which is caused by the uneven growth of cancer;
• quite often, with peripheral lung cancer, a “path” to the root of the lung is visible, caused by lymphangitis, peribronchial and perivascular tumor growth;
• X-ray examination in dynamics reveals progressive tumor growth. According to V. A. Normantovich (1998), in 37% of patients, tumor doubling occurs within 17-80 days; in 43% of patients - 81-160 days, in 20% of cases - 161-256 days;
• In advanced cases, the tumor compresses the corresponding bronchus, and atelectasis of the lung lobe develops.

More detailed radiographic signs of cancer and bronchial compression are revealed using X-ray tomography and computed tomography of the lung.

In the differential diagnosis of acute pneumonia and peripheral lung cancer, the following circumstances must be taken into account:

• in acute pneumonia, under the influence of rational antibacterial therapy, positive dynamics appear quite quickly - a decrease in severity and then complete disappearance of the darkening focus; in cancer, such dynamics are not observed;
• Acute pneumonia is characterized by a positive Fleischner symptom - good visibility of small bronchi against a darkening background; this sign is not observed in lung cancer;

Central cancer of the upper and middle lobe bronchi is manifested by darkening of the entire lobe or segment with a decrease in the volume of the lung lobe. X-ray tomography reveals the symptom of the stump of the lobar bronchus. Cancer of the main bronchus is characterized by varying severity of its stenosis up to complete stenosis with the development of atelectasis of the entire lobe of the lung. Stenosis of large bronchi is well detected by X-ray tomography and computed tomography.

An important diagnostic method is bronchographic examination, which reveals a rupture (“amputation”) of the bronchus when its lumen is blocked by a tumor.

Bronchoscopy

Bronchoscopy with multiple biopsies of the bronchial mucosa is of great importance in the diagnosis of lung cancer. During bronchoscopy, direct signs of lung cancer can be detected: endobronchial, endophytic or exophytic tumor growth, infiltrative changes in the bronchial wall. A tumor growing peribronchially is manifested by indirect signs: protrusion, rigidity of the bronchial wall, looseness of the mucous membrane, indistinctness of the pattern of cartilaginous rings of the lobar and segmental bronchi. Along with a biopsy of the bronchial mucosa, a bronchial wash is performed with subsequent cytological examination of the wash.

In 1982, Kinsley et al. described a method of fiberoptic bronchoscopy with simultaneous ultraviolet irradiation of the bronchial mucosa. The method is based on the fact that bronchogenic cancer cells have the ability to selectively accumulate a hematoporphyrin derivative compared to healthy tissues and then fluoresce in ultraviolet rays. When using this technique, the fiberoptic bronchoscope is equipped with a special ultraviolet irradiation source, a light guide, a filter, and a focused image amplifier.

In some cases, during bronchoscopy, a transbronchial puncture biopsy of a lymph node suspected of metastasis is performed.

Cytological examination of sputum

It is necessary to test sputum for cancer cells at least 5 times. Cancer cells can be detected in sputum in 50-85% of patients with central and 30-60% of patients with peripheral lung cancer.

Cytological examination of pleural effusion

The appearance of exudative pleurisy in lung cancer indicates an advanced tumor process. In this case, the pleural fluid often has a hemorrhagic character, and tumor cells are detected during cytological examination.

Fine-needle biopsy of palpable peripheral lymph nodes

Palpable peripheral lymph nodes (cervical, axillary, etc.) indicate metastasis of lung cancer. Puncture biopsy of these lymph nodes verifies metastasis of cancer in 60-70% of patients.

Immunological diagnostic methods

Immunological methods of cancer diagnostics have not yet received wide clinical application. However, according to literature data, in the complex diagnostics of lung cancer, the detection of tumor markers in the blood may have a certain diagnostic value: cancer-embryonic antigen, tissue polypeptide antigen, lipid-bound sialic acids. It is necessary to take into account the non-specificity of these tumor markers, they can be detected in the blood in cancer of other organs (liver, stomach, etc.).

Transthoracic puncture

Transthoracic puncture is performed under X-ray television control and is the main method for verifying the diagnosis of peripheral cancer, confirming the diagnosis in 65-70% of cases.

Acute appendicitis

The need for differential diagnostics of acute appendicitis and pneumonia arises when it is localized in the lower lobe of the right lung. This is more often observed in children. Right-sided lower lobe pneumonia is often accompanied by pain and muscle tension in the right half of the abdomen, including in the right iliac region.

The main differential diagnostic differences between right-sided lower lobe pneumonia and acute appendicitis are as follows:

• in pneumonia, the pain in the right iliac region does not increase when moving the hand deeper during palpation of the abdomen; in acute appendicitis, the pain increases sharply, and the tension in the abdominal muscles also increases;
• with pneumonia, pain increases with breathing, with acute appendicitis this connection is not typical or is poorly expressed; however, with coughing, abdominal pain increases both with pneumonia and with acute appendicitis;
• in acute appendicitis, the temperature in the rectum is significantly higher than the temperature in the axillary region (the difference exceeds GS), in acute pneumonia there is no such pattern;
• Careful percussion and auscultation, X-ray examination of the lungs reveal symptoms of acute pneumonia in the lower lobe of the right lung, which serves as the main criterion for differential diagnosis.

Cardiogenic pulmonary edema

The need for differential diagnostics of pneumonia and cardiogenic pulmonary edema ("congestive lung") is explained by the presence of similar symptoms: cough with sputum (sometimes with blood), shortness of breath, crepitations and fine bubbling rales in the lower parts of the lungs. The following circumstances serve as differential diagnostic differences:

• the presence of symptoms of decompensated cardiac diseases (heart defects, post-infarction cardiosclerosis, severe arterial hypertension, diffuse myocarditis, exudative pericarditis, etc.) in patients with “congestive lungs”;
• with “congestive lungs”, as a rule, an increase in the size of the heart is detected, atrial fibrillation is more often detected, episodes of cardiac asthma and pulmonary edema are observed (the clinical picture of these conditions is described in the chapter “Acute circulatory failure”);
• pulmonary edema almost always occurs as a bilateral process; during auscultation of the lungs, crepitations and fine bubbling rales are heard in the lower parts of both lungs;
• X-ray changes in the lungs during congestion depend on the degree of expression of the congestion process. At the stage of interstitial edema, an increase and deformation of the pulmonary pattern is revealed, due to the shadows of the longitudinal projections of the overfilled small vessels. With further progression of congestion and filling of the alveoli with transudate, bilateral darkening (often rounded) without clear boundaries appears, mainly in the medial areas of the middle and lower fields. With significantly pronounced congestion, an increase in the roots of the lungs is determined - they acquire the shape of a butterfly;
• congestion in the lungs develops, as a rule, against the background of other clinical manifestations of circulatory failure (pronounced peripheral edema, ascites, enlarged painful liver);
• in the absence of concomitant pneumonia, congestion in the lungs is not accompanied by pronounced laboratory signs of inflammation;
• changes in the radiograph of a congestive nature are significantly reduced and may even disappear completely after successful treatment of heart failure;
• Sometimes in the sputum of patients with congestion in the lungs, alveolar epithelial cells are found, the protoplasm of which contains an excess of phagocytized grains of the hemoglobin derivative - hemosiderin.

The above signs allow one to differentiate pneumonia from congestion in the lungs. However, it should be taken into account that pneumonia can develop against the background of congestion in the lungs. In this case, radiologically, an asymmetric darkening is detected most often in the lower lobe of the right lung, and laboratory signs of an inflammatory process appear.

Pneumonitis in systemic vasculitis and diffuse connective tissue diseases

In systemic vasculitis and diffuse connective tissue diseases, focal darkening in the lower parts of the lungs or peribronchial, perivascular infiltration, and increased pulmonary pattern may be observed. In differential diagnostics with pneumonia, attention should be paid to the characteristic clinical manifestations of systemic vasculitis and systemic connective tissue diseases (systemicity of the lesion, joint syndrome, usually involvement of the kidneys in the pathological process, skin erythematous, hemorrhagic rashes, etc.), corresponding laboratory manifestations, ineffectiveness of antibacterial therapy and the positive effect of treatment with glucocorticosteroids.

Etiological diagnosis

Currently, the problem of timely and successful etiological diagnostics has become extremely urgent. Accurate etiological diagnosis is the key to correct and successful treatment of pneumonia.

The main methods for establishing the etiological diagnosis of pneumonia are:

• A thorough analysis of the clinical, radiological and laboratory features of pneumonia depending on its etiology.
• Microbiological examination of sputum, sometimes bronchial lavage, pleural effusion with quantitative assessment of the microflora content. Sputum should be collected in a sterile container after preliminary rinsing of the oral cavity. To increase the effectiveness of the study, it is advisable to first process the sputum using the Mulder method. To do this, take a purulent piece of sputum and thoroughly wash it in a sterile isotonic sodium chloride solution sequentially in three Petri dishes for 1 minute in each. This helps remove mucus from the surface of the sputum lump containing the microflora of the upper respiratory tract and oral cavity. It is advisable to take at least three lumps from different parts of the sputum. After this, sputum is sown on elective biological media. The number of microbial bodies in 1 ml of sputum is also counted.

The causative agents of pneumonia in this patient are considered to be those microorganisms that are isolated from sputum in the amount of 1,000,000 or more microbial bodies in 1 ml.

Simultaneously with sputum seeding on elective biological media, sputum smears are made with subsequent bacterioscopy. One smear is stained using the Romanovsky-Giemsa method for cytological analysis (the type and number of leukocytes, the presence of bronchial, alveolar epithelium, erythrocytes, atypical cells, etc. are determined). The second smear is stained using Gram and the abundance of microflora, the presence of gram-positive and gram-negative microorganisms, their intra- or extracellular localization are assessed. But first, it is necessary to establish whether the preparations belong to sputum, and not to the oral mucosa. The criteria for Gram-stained preparations to belong to sputum are:

• the number of epithelial cells, the main source of which is the oropharynx, is less than 10 per total number of cells counted;
• predominance of neutrophilic leukocytes over epithelial cells;
• the prevalence of microorganisms of one morphological type. Bacterioscopy of sputum smears stained by Gram allows one to tentatively assume the causative agent of pneumonia. Thus, if gram-positive diplococci are detected, one should think about pneumococci; chains of gram-positive cocci are characteristic of streptococci, clusters of gram-positive cocci - for staphylococci; short gram-negative rods - for Haemophilus influenzae; in addition, gram-negative microorganisms include Moraxella, Neisseria, Klebsiella, Escherichia coli.

Immunological studies. Immunological methods that allow verification of the causative agent of pneumonia include detection of bacterial agents using immune sera in the counter immunoelectrophoresis reaction; determination of titers of specific antibodies (using enzyme immunoassay, indirect hemagglutination reaction, complement fixation reaction). The role of determining specific antibodies in the blood serum is especially important when using the paired serum method (a significant increase in the antibody titer during a repeat study after 10-14 days compared to the titers obtained at the onset of the disease).

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