Contents
Diagnosis of pulmonary tuberculosis
When visiting the patient, the doctor will:
- examines the lymph nodes,
- listens to the lungs with a stethoscope to hear the lung sounds during breathing.
First of all, it is necessary to determine whether the patient suffers from this disease if he:
- suffered from pleurisy as a child;
- originates from an area of distribution of the disease.
Examinations for pulmonary tuberculosis
Mendel-Mantoux test
The most common component of tuberculosis diagnostics is a skin test.
Theory of the Mendel-Mantoux test after an article by Surajit Nayak and Basanti Acharjya, which was published in the “Indian dermatology online journal”.
The reaction to the tuberculin injected into the skin is a classic example of a delayed cell hypersensitivity reaction.
The T-lymphocytes sensitized by a previous infection are called to the skin area where the injection took place.
There they release lymphokines, which are substances that promote and coordinate the immune reactions of the cells.
These lymphokines cause:
- local dilation of blood vessels (vasodilation),
- Oedema
- fibrin deposition,
- Attracting other inflammatory cells to this region.
The result is hardening of the skin and the formation of a rash.
Typical for the reaction:
- delayed onset: the peak is reached no earlier than 24 h after injection of the antigen;
- skin hardening;
- in rare cases, the formation of vesicles and necrotic areas.
Procedure
The doctor injects a small amount of a test substance called PPD under the skin on the forearm.
Within 48-72 hours:
- examine the patient’s arm,
- he checks whether a rash has occurred.
A hard red and raised spot indicates a positive test result for infection by Mycobacterium tuberculosis.
This means that the patient has come into contact with this bacterium.
The test does not indicate whether it is a latent or active infection.
Laboratory diagnosis of pulmonary tuberculosis
Blood tests can help confirm or rule out latent or active tuberculosis.
These tests use sophisticated techniques to determine the immune system’s response to TB bacteria.
The number of white blood cells is increased.
The QuantiFERON test is performed to determine the concentration of gamma-feron or IFN-γ in the blood and is more accurate than the skin test on the arm.
Examination of expectorate or sputum
If the chest scan shows signs of tuberculosis, the doctor may bring a sample of the sputum (expectorate) that is ejected when coughing for examination.
This research is helpful to:
- determine the occurrence and nature of the bacterium,
- determine the appropriate antibiotic treatment.
In the laboratory tests you can see:
- the rod with intact microbacterium (figure bottom left),
- the digestive fragments of the microbacterium, if it is located in the macrophages (figure below right).
The polymerase chain reaction (PCR) is a method for amplifying the genetic material DNA and helps in the search for the specific fraction of the tuberculosis microbacterium, the sequence IS6110 (this is the most detailed examination).
Chest X-ray in pulmonary tuberculosis and CT
If the Mendel-Mantoux test is positive, the doctor orders a chest X-ray (chest X-ray).
The X-ray may show white spots in the lungs that look like cotton.
They are usually located in the tip of the lung (apical region).
In very few cases, primary TB can be detected on an X-ray, especially if it leads to a strong infection of the lymph nodes in the tissue space of the chest cavity (mediastinum) when the microbacterium is transported to the lymphatic nodes of the hilus with lymphatic drainage.
In children, enlarged lymph nodes, as shown in the figure on the right, may be an indication of:
The lung hilus no longer has its typical line shape, but is enlarged.
The figure on the left shows an enlargement of the lymph nodes and atelectasis (the individual alveoli cannot be seen).
Sometimes the lymph nodes become very large, compressing the walls of the bronchi, which are very soft in children.
The result is a blockage of air circulation, causing the atelectasis of a lobe of the lung.
When interpreting the X-ray, the following must be taken into account:
The effects of TB can be seen in the more ventilated lung sections because:
- the disease is transmitted through the inhaled air particles, the microbacterium is located where it is inhaled;
- in these sections there are fewer defense cells of the immune system.
These preferred areas are located at the tip and back of the upper lobes of the lung as well as at the tip of the lower lobe of the lung.
Tuberculosis can present itself in two different ways in terms of symptoms and X-rays:
1) Exudative form, in which the alveoli are affected and bright, converging spots can be detected. The image on the left shows a white spot at height:
- the lower tip of the lung lobe,
- of the left upper lobe of the lung.
As a rule, the bacterium is inactive in these segments.
There is satellite mediastinal adenopathy, the mediastinum is very wide and shows a roundish appearance on the right side.
The pulmonary hilus has an enlarged volume or lymph nodes of the mediastinum (in the chest cavity), which changes the normal radiological appearance of the thorax.
On the right picture you can see a roundish space between the trachea and the right edge of the lungs. In this case, it is relatively easy to detect an enlargement of the lymph nodes, with a vast bright area at the level of lung tissue.
Such an X-ray image is not only available in the case of TB but also in lung cancer.
2) Fibrous-cheesy form, in which necrosis predominates, which progresses until it reaches a bronchi. From here, the contents of the tubercle are excreted by air by cough. This leads to the formation of “tubercle caverns“, which are structures with:
- a relatively thick wall,
- a radio-transparent center (on the X-ray image it appears black).
A pulmonary compaction (bright spot) is formed, which extends to the bronchi, where the necrotic material is eliminated. In the horizontal CT section (right figure) you can see the formation of caverns in the affected areas, i.e. cavities with their own wall.
The forming cavern differs significantly from a cyst in appearance:
- A cyst has very thin walls.
- In the tubercle caverns, the walls are thick, about 1.5-2 cm wide.
The incoming air accumulates higher up than the liquid material of the casing necrosis, thus forming a “meniscus” between air and necrosis, i.e. a water-air layer.
This can be seen much better with a CT than on an X-ray.
Lung neoplasms that cause (ischemic) necrosis and touch the bronchi show a similar X-ray and CT.
When the bacterium enters the bloodstream, it is called miliary tuberculosis.
In this case:
- the bacterium spreads,
- settles everywhere in the lungs,
- causes numerous micronodular opacities scattered throughout both lungs.
These opacities correspond to granulomas in the lung interstitium, with tiny nodules.
The images obtained during X-ray examinations of miliar TB can also be seen in rare cases in other diseases, such as:
- Micrometastases
- Pneumonia caused by varicella
The tiny nodules can flow together and form much larger opacities called tuberculomas, as the right CT scan shows, in the subpleural space.
Patients with miliary tuberculosis: Sometimes it is extremely difficult to detect this type of tuberculosis on the X-ray, but the CT shows a figure that resembles the branch of a tree (bronchi) with all its small flowers (micronodules) flanked by the bloodstream, also called “tree in bud” (left figure).
This means that the patient actively eliminates the bacteria.
More and more often there are older people who had TB in their youth and in whom you can now see the results (consequences):
- You suffer from fibrosis (formation of scar tissue).
- The lungs become misshapen and distorted in the affected areas (typically in the upper lobes of the lung).
CT shows the deformation of the parenchyma with interstitial fibrotic opacities in the lungs.
The hili may be pulled upwards, usually located around the middle of the lungs, but in these cases they can reach below the collarbone.
Calcifications can form in the scar tissue.
Treatment of tuberculosis
Most patients with TB can be cured. However, drug therapy must not be discontinued before the prescribed date.
This could leave behind a bacterial strain resistant to TB drugs that is extremely difficult to treat.
Treatment of patients with latent infection
Treatment is only given to people at risk of progression, such as people with weakened immune systems, etc.
The most commonly used drugs to treat active TB are:
Isoniazid (INH) is one of the most commonly prescribed medications.
This is a low-cost drug that is sufficient to cure most TB cases.
Preventive treatment with INH is recommended for people:
- who are in close contact with an infected person;
- who were found to have a positive Mendel-Mantoux test and an abnormal X-ray horax indicating latent TBC;
- whose tuberculin test has been positive in the last two years;
- who have a positive Mendel-Mantoux test and another disease at the same time (for example, AIDS or diabetes), or corticosteroids
Rifampicin (Rifinah®) is one of the most commonly prescribed medications. But due to the increasing resistance of bacteria to the drugs, the doctor often prescribes in addition:
- pyrazinamide,
- streptomycin sulphate,
- Ethambutol.
About one in seven tuberculosis sufferers have bacteria that are resistant to drugs that previously cured the disease.
Resistance occurs when patients have not been able to complete drug therapy, which lasts at least six months.
Multi-resistance
One problem in the treatment of tuberculosis is multidrug, with two cases:
- Primary resistance: is already present in the strain responsible for the infection;
- Secondary resistance: occurs during the course of treatment.
For this reason, it is always necessary to create an antibiogram (laboratory test to determine the sensitivity of a bacterium to an antibiotic) to find out whether the bacillus is multi-resistant.
In pregnancy, tuberculosis does not lead:
- Premature birth
- Miscarriage.
The patient can be cured with the antibiotics prescribed by the doctor.
How long does tuberculosis last? Prognosis
The recovery time with therapy is about 6 months.
Long-term consequences
Patients always heal with sequelae:
- Calcifications
- Fibrothorax (pleural fibrosis)
- Calcifying pleurisy
- Caverns created by drainage of granulomine content.
In the past, some people who did not take antibiotics developed a form of chronic tuberculosis.
Vaccination against tuberculosis
When vaccinating against tuberculosis, a medicine called Bacillus Clamette-Guérin (BCG) is used.
Unfortunately, it is not very effective (only in about 50% of people). In fact, TB can be contracted even after vaccination.
Vaccination protection decreases over time.
Groups of people who should be vaccinated are those at increased risk, specifically:
- newborns (at risk of meningitis),
- medical staff,
- Employees in prisons or institutions where tuberculosis patients are staying.
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