Tuberculosis is an infectious (able to spread from a sick person to a healthy one) disease caused by a specific pathogen – bacteria Mycobacterium tuberculosis. Animals can also suffer from this disease (cattle, chickens, rodents, etc.).
The most common cause of the disease in humans is the following species of bacteria:
1. Mycobacterium tuberculosis humanus is the most common subspecies. It is this micro-organism that causes disease in 85% of cases of tuberculosis.
2. Mycobacterium tuberculosis bovines. It is becoming the main cause of TB in cattle. Fifteen percent of all TB cases in people are accounted for this pathogen. It is worth noting that this particular bacterium has become a source for the synthesis of the BCG vaccine.
3. Mycobacterium tuberculosis microti. It is a rare human pathogen, but quite common among rodents.
4. Mycobacterium tuberculosis africanus is a regional subspecies which is dangerous only in African countries, where it becomes the cause in 90% of cases.
- Factors contributing to the development of pulmonary tuberculosis
- Classification of pulmonary tuberculosis
- Complications of pulmonary tuberculosis
- Treatment of pulmonary tuberculosis
According to the World Health Organization, one third of the world’s population is infected with tuberculosis. This means that the mycobacterium is already in the human body but the disease is still “dormant”. Each year 8-9 million people are suffering from the acute form of the disease. The number of deaths from complications of tuberculosis reaches up to 3 million people a year.
The pathogen can enter the body through air, contact (through things used by the patient) and food (milk from a sick cow, eggs, etc.). The microorganism is very stable in the environment; in a humid climate it remains viable throughout the year.
A distinctive feature of Mycobacterium tuberculosis is an extremely volatile virulence. This means that the microorganism responds to the state of resistance of the host’s body.
A variety of reactive human responses to Mycobacterium tuberculosis determines multiple clinical and morphological manifestations of the disease.
While being idle in the normal immune system condition, pathogen multiplies rapidly and becomes aggressive at the slightest decrease in its level. In may take up to ten years from the moment of infection before the first clinical manifestations appear.
The main processes that occur in the affected organ at the tissue (histology) level after the penetration of the pathogen are:
- Infiltration. Arrival of the pathogen to the place of discovery of “foreign agent” of blood cells (macrophages, lymphocytes, neutrophils) responsible for its neutralization.
- The death of the soft tissues surrounding the cluster of mycobacteria.
- Duplication of mycobacteria and their distribution via the stream of lymph to distant organs.
- Activation of the immune system in order to remove the dead tissues and replace them with scar tissue (sclerosis). This can be the final process of the disease proving the death of all mycobacteria, but it can also serve to limit the surviving bacteria from healthy cells and the entire organism. In the second case, the vital activity of bacteria is maintained, and they can cause further aggression at any moment.
The sequence of these processes is constantly disrupted. Sometimes you can see scarring and fresh foci of tissue necrosis on the same organ.
The main and most common form of human TB is pulmonary tuberculosis. The particular importance of this form of the disease is that it is the leading source of spread of TB due to contamination of the patient’s surrounding space when talking, coughing.
At the same time, we must remember that pulmonary tuberculosis is a particular manifestation of the infection of the whole organism. So there are various combinations of infection of lungs and other organ systems.
The practical value in predicting the severity of changes in the lungs are the individual characteristics of the causative agent (aggressiveness, sensitivity to antibiotics), the amount of the microbial mass in the infection, the condition of the immune system of the infected and other.
1Factors contributing to the development of pulmonary tuberculosis
1. The weakening of the immune system due to various factors such as:
- chronic stress and fatigue;
- inadequate and poor nutrition;
- receiving steroid hormones, cytostatics and immunomodulators in combination with severe pathology (system and oncological diseases, conditions after organ transplantation);
- HIV infection.
2. Low standard of social and living conditions and particularities of life. For example, penitentiaries; cities with a high population density; people leading asocial way of life associated with vagrancy; migrants; drug addicts; mentally ill patients fall into the risk group. This same risk group includes health workers.
3. Chronic alcoholism.
4. Chronic inflammatory diseases of the lungs and upper respiratory tract.
6. Chronic heart diseases
2Classification of pulmonary tuberculosis
There is primary and secondary pulmonary tuberculosis.
The disease develops immediately after the contamination and is quite active due to severe immune system reaction to the pathogen. The most common areas of affection in the lungs are the easily ventilated areas, such as III, VIII, IX and X segments of the right lung. The affected area necrotizes at once, taking a typical cheesy appearance. The very area of necrosis, inflammatory swelling around it and tuberculous lymphangitis, radiologically manifested as strands from the foci to the hilar lymph nodes of the lung is called “primary tuberculosis affect.” This particular X-ray symptom of the primary pulmonary tuberculosis is always detected.
The outcome of the affection of the primary lung is:
1. The growth of necrotic and inflammatory processes involving the new sections of the lungs, followed by lymphatic or hematogenous spread of the process to other organs and systems.
2. Full recovery with scarring of the primary affect. Calcium salts can be deposited in varying amounts in the scarred area, which in severe cases is determined by X-ray as a “signiture” of a previously existing latent form of tuberculosis. They are called Gohn foci.
3. Chronic tuberculosis. This means the occurrence of a cavity close to the process, periodic worsening of tuberculosis to the form of caseous pneumonia, the expansion of the zone of the primary affect and the presence of permanent intoxication. The process may spread to the pleura, causing tuberculous pleurisy. Chronic primary tuberculosis is characterized by the fact that it affects only one lung.
Generalization and chroncalization of primary tuberculosis is most common in adults.
In childhood it is common that in most cases the healing process involves scar formation. The disease looks like flu or occurs under the guise of lung bronchitis.
Secondary pulmonary tuberculosis
The disease does not provide stable and permanent immunity, as some other infectious diseases. After some time, under certain conditions and factors which we discussed above, there is nothing stopping a person to get ill with TB again. The cause may be the remaining lung tissue at the site of the primary focus of viable Mycobacterium tuberculosis, as well as new microorganisms, received from the outside. This will be called the secondary pulmonary tuberculosis.
The spread of TB in the lung may be of bronchogenic or lymphatic nature.
The difference between the secondary and the primary processes is the absence of the previously described primary affect.
The most practical application found the classification which incorporates the histological changes and can be seen on the X-ray examination. Almost all of the above forms are specific for secondary form of pulmonary tuberculosis.
Clinicopathologic classification of pulmonary tuberculosis
1. Acute miliary tuberculosis
2. Hematogenous disseminated pulmonary tuberculosis
3. Focal pulmonary tuberculosis
4. Infiltrative-pneumonic pulmonary tuberculosis
5. Lung tuberculoma
6. Caseous pneumonia
7. Cavernous lung tuberculosis
8. Fibrous-cavernous pulmonary tuberculosis
9. Tuberculous pleurisy
10. Cirrhotic tuberculosis
11. Other forms (tuberculosis in combination with occupational affection of the lungs and other.).
Patients can have mild, moderate and severe tuberculosis. If there are complications, depending on the possibilities of correction there can be outlined a compensated, decompensated or subcompensated processes.
In addition, depending on the inoculation of Mycobacterium tuberculosis from sputum, there exist open, closed and the form of the disease with periodical release of Mycobacteria.
The disease can occur implicitly, with general manifestations and complaints:
- weakness, chronic fatigue;
- night sweats;
- causeless low-grade (about 37 ° C) temperature;
- lack of appetite;
- weight loss;
- general paleness.
The disease at this stage can only be identified during the implementation of fluoroscopy or X-ray examination of the chest due to other reasons.
The first sign that makes the doctor suspect something is wrong is an increased size of lymph nodes of axillary, supraclavicular or cervical groups. It is worth emphasizing that the enlarged lymph nodes are often limited to only one area. Nodes are not connected to each other and to the surrounding tissue, they are painless. At the same time, the CBC remains without marked changes specific of inflammation. On the contrary, the blood test shows anemia and reduction of leucocytes (leykotsitopeniya).
The clinical picture of pulmonary tuberculosis may vary depending on the amount of the invaded tissue.
All forms of pulmonary tuberculosis are characterized by the following features:
1. Cough. From dry to wet, with a massive amount of phlegm. Sputum may have cheesy or purulent appearance. When there is blood in the sputum, it looks “rusty” (hemoptysis).
2. Shortness of breath (feeling of shortage of air). Due to the reduction of the respiratory surface of the lung during inflammation and scarring.
3. Measurement of sound on percussion (tapping) of the chest wall. Dullness of sound is detected over the areas of inflammation and the formation of scar tissue, pleural effusion, filling of the cavities with liquid content. “Boxed” sound – in a projection of formed hollow cavities.
4. The occurrence of wheezing sounds during auscultation (listening) of lungs. Their characteristics and intensity varies. There is dry and wet wheezing. You can hear special “amorphous” type of breathing above the cavities. In some areas breathing can be significantly weakened.
5. An increase of body temperature. The temperature can rise up to 41°C if TB is in aggressive and developing forms. Fever becomes permanent or manifesting significant extremes, falling briefly to 35-36°C. When TB is not in the acute form, temperature does not exceed 37-37,5 ° C, and increases, usually in the evening.
6. Weight loss. The patient can lose up to 15 kilograms or more.
7. Pain in the chest. Joins at deployed stages of the disease and invasion of tuberculousis into the pleura.
Primary pulmonary tuberculosis:
1. The prevalence of general symptoms.
2. Coughing occurs when the disease progresses.
1. Multiple lesions in the lungs on both sides.
2. The disease can occur acutely with severe symptoms of intoxication and high degrees of severity. Furthermore, there exist subacute and chronic forms.
3. It occurs in individuals with a significant weakening of the immune system.
4. The size and type of isolated foci:
- miliary (up to the value of a pinhead);
- macrofocal (more than 1 cm in diameter);
- cavernous (involves cavities).
5. In addition to the pulmonary tuberculousis the inflammation can be detected in heart, brain and its membranes, in large joints and bones, spleen, liver and kidneys.
6. Light forms of miliary tuberculosis may take place under the disguise of a cold. The only difference is that, unlike the latter, feeling of unwellness persists for a long time.
7. In severe forms, along with cough, dyspnea, sputum and chest pain, to the foreground gradually emerge manifestations of lesions of other organs: severe headache, dizziness and cramps if the CNS is affected; limitation of motion and pain in the joints if the bones and joints are affected, etc. The pronounced intoxication syndrome adds up.
1. On the X-ray it is characterized as a group of lesions of the lung tissue from a few millimeters to centimeters in diameter.
2. Clinically it resembles pneumonia or bronchitis, but unlike them it is characterized by a prolonged duration and blood in the sputum.
Infiltrative-pneumonic pulmonary tuberculosis:
1. It comes out in exacerbation of the inflammatory process around the existing focus.
2. Occurs in secondary tuberculosis.
1. X-ray picture is similar to the signs of lung cancer – hence the name.
2. Small infiltrates remain for quite a long time and do not lend themselves to anti-inflammatory treatment, which suggests that it has the tumor origin.
1. Characterized by an aggressive course: spread areas of lung tissue inflammation fuse together in a short time, forming a field of caseous necrosis.
2. Often, the first manifestation is hemoptysis, after which the temperature rises sharply and other common pulmonary symptoms add up.
3. Necrotic areas quickly melt, forming cavities.
4. Can occur during the primary and secondary tuberculosis.
5. Characterized by frequent complications of pulmonary hemorrhage and spontaneous pneumothorax (if it broke in the pleura).
Fibrous-cavernous pulmonary tuberculosis:
1. The result of the development of destructive forms of pulmonary tuberculosis.
2. X-ray determines single or multiple cavities with a dense wall formed as a result of sclerotic processes. Besides the oral capsule, a part of the surrounding lung tissue is also subjected to diffuse fibrosis, replacing the alveoli with thick scars, thereby greatly reducing the respiratory surface area.
3. You can define bronchogenic spread of infection in the presence of it in the affected area. In these cases, there appear new lesions of various diameters and time of development in the peribronchial space.
1. Appears as a complication of other forms of TB in the form of spreading of the process to serous coat of lungs.
2. Develops through contact (with focus location in the immediate vicinity), hematogenous or lymphatic routes of infection.
3. Tuberculous pleurisy may be dry (with fibrin deposition and minimal liquid component) and exudative (with the presence of fluid of serous or purulent character).
Cirrhotic pulmonary tuberculosis:
1. The result of the massive destruction of the lungs in the absence of adequate treatment of destructive forms.
2. The presence of other chronic inflammatory diseases of the lung is considered to be the additional risk of getting tubercular cirrhosis.
3. It is a rare form of TB because the majority of patients do not live that long.
4. As a result of the destruction a considerable area of the lungs is replaced by connective (scar tissue).
5. However, despite all this, the foci of the stored tubercular inflammation are identified in the lung tissue.
6. It is accompanied by signs of severe respiratory and heart failure.
4Complications of pulmonary tuberculosis
1. Pulmonary hemorrhage. Its massiveness and technical difficulties in its cessation are often the cause of death.
2. Spontaneous pneumothorax. During cavernous forms of TB the penetration of large amount of air into the pleural cavity can lead to a shift of the mediastinum and reflex cardiac arrest.
3. Tuberculous pleurisy. Exudative forms, showing a gradual accumulation of fluid in the pleural cavity, may as well lead to the progression of respiratory and subsequent heart failure.
4. Generalization of the process by hematogenous spread with the development of tuberculous sepsis.
5. The development of chronic “pulmonary heart” by increasing the pressure in the pulmonary circulation with significant changes in the tissues of the lungs.
5Diagnosis of pulmonary tuberculosis
Polyclinic, dispensary stage.
1. History of the disease and complaints.
2. Physical examination (percussion of lungs, auscultation, palpation of regional lymph node available for palpation).
It should be noted that in the early stages of the disease and the existence of small lesions information value of physical methods is quite low.
3. Complete blood and urine analysis.
4. Examination of exudated mucus under a microscope.
Ziehl-Neelsen stain method allows to see if any of the pathogen is present. This study, in the presence of negative results, is carried out three times.
5. Chest X-ray.
To get more information it is better to use the forward and side view.
6. Mantoux test.
It is performed annually as a method of screening for health examinations during childhood and adolescence. The adults do it according to indications.
Evaluation results after 72 hours after intradermal injection into a forearm:
- a negative reaction – in the presence of a point in the injection site not more than 2 mm in diameter;
- doubtful reaction – in identification of a clearly limited round spot 2-4 mm in diameter or a diffuse light redness of the skin of any size;
- positive reaction – spot of 5-17 mm in diameter in children and adolescents, and 5-21 mm in adults;
- hyperergic response – a papule more than 17 mm in diameter in children and adolescents and more than 21 mm in adults.
Infected with TB are:
- Persons who for the first time revealed a positive reaction (aka: turn of tuberculin sensitivity);
- Persons with a 6 mm increase in doubtful or positive reaction;
- Persons with hyperergic reaction (in this case, the primary TB disease is likely to be present).
7. Sputum culture for growth media, with the simultaneous examination for sensitivity to antibiotics.
8. Study of sputum for PCR.
It is a quick way to determine the presence of mycobacteria by the reaction to the antigen.
9. ELISA blood test to detect TB antigens and antibodies.
10. CT scan of the lungs.
11. Ultrasound examination for the presence of pleurisy and in identifying subpleural spaced formations.
These examinations are required to clarify the diagnosis by means of collection of material for cytological and histological examination to differentiate the tumor processes, the existence of which can occur together with or instead of the suggested TB.
1. Conduction of bronchoscopy with biopsy or bronchial lavage to latter study the lavage fluid (cytology, culture of growth media).
2. Puncture of the pleural cavity and pleural biopsy.
3. Thoracoscopy (examination of the pleural contents of the pleural cavity with an optical device) with biopsy of the lung.
4. Intraoperative open lung biopsy.
6Treatment of pulmonary tuberculosis
Treatment is carried out in a hospital and implies a fight against the causative agent of the disease, minimizing the sclerotic effects and prevention of complications.
Treatment includes therapeutic (conservative) and surgical methods.
Certain difficulties appear due to the emergence of new strains (varieties) of mycobacteria that show no reaction to antibiotics. This requires constant adjustment of the dosage and combination of different groups of antibiotics. It is necessary to conduct various studies in order to evaluate the effectiveness of treatment. Long-term treatment lasts up to one year. There are various treatment regimes involving various combinations of drugs, taking into account age and sex data.
In addition, antibiotic treatment is divided into two phases:
1. The initial (intensive) phase of treatment. The combination of antibiotics and doses aimed at effective suppression of mycobacterial multiplication rate with the rapid development cycle and preventing the development of drug resistance.
2. Phase of the ongoing treatment. It affects the intracellular mycobacteria and dormant forms of mycobacteria for the prevention of their multiplication. In this phase, other drugs that stimulate the regeneration process are added.
The presence of severe forms of tuberculosis requires that the patient stays in bed.
Meals include a special diet, rich in proteins. The goal of nutritional therapy – correction of metabolic disorders.
Collapse therapy is a special form of treatment of pulmonary tuberculosis not applicable to any disease. The point of the method is induction of artificial pneumothorax in order to compress the lung of the patient. As a result – the existing cavities subside, repair processes improve, and the risk of dissemination of the infection reduces. It is appointed in intensive pharmacotherapy stage.
Indications to collapsotherapy:
1. Destructive types of tuberculosis, with the presence of cavities with no signs of sclerosis.
2. Pulmonary hemorrhage (if the data on localization is reliable).
Artificial pneumothorax is mainly used in the intensive phase of treatment in pharmacotherapy.
Pneumoperitoneum is also useful (increasing of pressure in the abdominal cavity in order to lift the diaphragm and limit its mobility for the purpose of immobilizing the lungs).
Indications for pneumoperitoneum:
1. Cavernous tuberculosis.
2. Infiltrative tuberculosis with the presence of decay cavities.
This method is mostly used when the process is localized in the lower lobe.
Indications for surgical treatment of pulmonary tuberculosis:
2. The presence of single cavities.
3. Cirrhotic and cavernous changes within one or several lobes within the same lung.
In the presence of tuberculous pleural empyema, caseous pneumonia, caseous-necrotic lymph node affection the appointment of a surgical treatment is strictly individual.
Removal of the affected areas of lung is not carried out at the common processes, severe degrees of respiratory and heart failure.
7Prediction of pulmonary tuberculosis
The absence of treatment of the active process results in death in 50% of cases of pulmonary tuberculosis in the course of two years.
In the patients who survived, the process becomes chronic, with the continuing colonization of the surrounding space.
8Prevention of pulmonary tuberculosis
1. Vaccination (it refers to the specific preventive methods).
It is produced using a mild strain of Mycobacterium tuberculosis (BCG) in order to develop immunity. In case a vaccinated person gets ill with tuberculosis, it may develop in the mild form. The acquired effect is maintained for about 5 years on average. Vaccination is included into the planned immunization of children and is held in the first week after birth, latter it is repeated at the age of 7 and 14. According to indications, BCG vaccination can be performed every five years up to 30 years of age.
After BCG vaccination normal Mantoux test can be positive within the next 5-7 years, reflecting the presence of a good post-vaccination immunity.
Mantoux reaction in vaccinated is an indication of the remaining immunity to tuberculosis. Up to 7 years after vaccination Mantoux test can be positive.
It involves taking antibiotics according to the scheme. It may be primary (performed to the persons that are not infected but were in contact with an ill person) and secondary (not infected or those who recovered from TB).
- presence of household, family and professional contacts with patients who have an open form of tuberculosis;
- a person who showed a hyperergic tuberculin reaction during the Mantoux test;
- occurrence of tuberculosis-like changes in the lungs when taking steroids and other immune modulators for other diseases.
It is a screening method for the annual examination. It allows identify other non-specific lung diseases and tumors of the chest besides tuberculosis.
4. Changing of social factors that influence the incidence of tuberculosis (living conditions, prevention of occupational diseases, nutrition, combating alcoholism, etc.).