Can the CT do not show TB?
Detection of tuberculosis in its early stages – one of the main objectives of clinical examination. However, the methods of screening diagnostics that are used in the Protocol of prophylactic medical examination have limited diagnostic capabilities. Using fluoroscopy to detect the presence of changes in the pulmonary field, but it is impossible even approximately to judge about their nature. Plain radiography of the lungs is also not always accurate.
Computed tomography of the lungs along with microbiological examination of the sputum and Diaskintest can be used to confirm or exclude the diagnosis in controversial cases. If the diagnosis of tuberculosis is proved, CT assign to Refine the location and extent of distribution of specific inflammatory process.
In some cases, for the diagnosis of tuberculosis using CT?
CT is not a screening method for the diagnosis and is not used for routine detection of pulmonary tuberculosis. This study indicated for the clarification of the tests performed earlier, the size and location of the lesion or control treatment. Indications for lung computed tomography in the diagnosis of tuberculosis are:
- infiltrative shadow or other characteristic changes identified using fluoroscopy or survey radiography of the lungs;
- the positive result of Mantoux test or Diaskintest;
- a positive result of sputum culture for acid-fast bacilli, if CT or MRI was not performed before the test;
- refinement of the shape, position and prevalence of tuberculosis after pre-diagnosis;
- monitoring changes in the lungs and lymph nodes after treatment.
Changes in the computer tomogram in patients with a negative result of bacterial culture, tuberculin skin test, and Diaskintest should be interpreted as non-tuberculous lung lesion.
What changes are detected on CT scan in tuberculous process in the lungs?
In the acute phase of the process (primary tuberculous complex) CT shows one or more foci of the seal lung tissue, located close to the bronchi. In addition, the modified visible enlarged lymph nodes of the root of the affected lung and mediastinum. In patients with disseminated tuberculosis revealed multiple small foci of seals, mostly in the upper lobes of the lung.
The use of CT with intravenous contrast allows high probability to diagnose tuberculous lesions. In the phase of caseous necrosis contrast to actively accumulated in the shell of the lymph node but not in the middle. Similar changes in lung computed tomography allow with high probability to assume the existence of tuberculosis, but did not confirm the diagnosis. No changes in the lungs does not exclude extrapulmonary form of tuberculosis.
Changes on lung CT scan do not give grounds to confirm the diagnosis, as they can have non-tubercular nature. The use of intravenous contrast and CT increases the diagnostic accuracy.
Scars formed on the location of foci of tubercular decay after treatment are also visible on CT with high resolution. To get the most accurate results it is recommended to perform CT of the lungs or, at least, the scanning apparatus of the spiral type. To confirm the lack of activity of the process in the presence of «old» changes on CT can be used or tuberculin skin test Diaskintest (it should be negative).
Tomography in the diagnosis of extrapulmonary forms of tuberculosis
In addition to pulmonary tuberculosis, meet extrapulmonary forms of the disease. This defeat of bones and joints, including joints of the spine (tuberculous spondylitis); of the urinary organs or soft tissues. While clinical symptoms may be nonspecific, with many similarities to inflammatory processes of different origin. In this case, the changes identified by CT, help to suspect the tubercular process, or to determine its localization, if the preliminary diagnosis was based on positive tuberculin or Diaskintest.
In addition to pulmonary tuberculosis, there are extrapulmonary forms of the disease, so the absence of changes on CT of the lungs with a positive laboratory test (the Mantoux test and Diaskintest) indicates the need to search for extrapulmonary lesion.
CT has high informative value for diagnosis of tuberculous lesions of the kidneys. On the CT you can see the pockets seal tissue with a characteristic accumulation of the contrast. In addition to imaging of the affected organ must be done lung CT scan to confirm the presence of the primary tumor is one of the criteria for the diagnosis of tuberculosis.
Is it possible for the CT to confirm or refute the diagnosis?
Diagnosis of pulmonary tuberculosis and extrapulmonary localization includes several stages, the final diagnosis is made by combination of clinical examination, laboratory and instrumental methods. CT, especially MSCT, allows with high probability to assume the existence of a tuberculous process, based on the specifics identified in the images changes. However, this is not enough to establish a definitive diagnosis.
No change also gives the right to exclude the diagnosis. If CT light is not detected any changes, but the result of the Mantoux test or positive Diaskintest, there may be extrapulmonary lesions in the active phase currents. A negative index Diaskintest if there are changes on CT scan, most likely indicates a non-tuberculous nature of the process, as this test has very high diagnostic accuracy.
In addition to changes on the radiograph or CT scan is necessary to confirm the results of laboratory tests:
- General clinical analysis of blood with definition of nuclear shift of neutrophils. In the active phase of tuberculosis the number of neutrophils in the blood increased, and an increased number of young forms of these cells. With chronicity of the process quantitative shift may be small, but the shape of their nuclei.
- Mantoux test or Diaskintest is allegoria, which shows the presence in humans of Mycobacterium tuberculosis and how active it caused by the pathological process. Diaskintest has a higher diagnostic accuracy, as contains only antigens of pathogenic mycobacteria and gives the minimum number of false positive results.
- The sputum culture for the presence of acid-fast forms of mycobacteria is carried out to determine the activity of tuberculosis and confirmation of diagnosis. This test is included in the compulsory examination report in tuberculosis, but the information content of the result depends on the correctness of a fence of material for research. If mucus is not secreted abundantly, the patient is often unable to collect it in the test tube is clean saliva. Culture test result may be negative even when there are obvious changes in the pictures and positive Diaskintest. In this case, diagnosed a closed form of tuberculosis.