Instrumental imaging methods
The choice of a specific patient examination method is strictly tied to the suspected localization of the pathological process. The clinician has three main groups of instrumental studies at their disposal:
- Radiological imaging. Includes classical baseline radiography, as well as high-tech methods: computed tomography (CT) and magnetic resonance imaging (MRI). If necessary, these studies are supplemented with contrast enhancement for a more precise assessment of anatomical structures.
- Endoscopic methods. This approach is used when a visual assessment of the internal surfaces of hollow organs is required, as well as examination of the airways.
- Ultrasound examination (ultrasound). Traditionally acts as the method of choice if the physician suspects an extrapulmonary (non-pulmonary) lesion. Such localizations include the abdominal organs, kidneys, and joints.
Criteria for an absolutely reliable diagnosis
Despite the wide variety of imaging methods, they provide only an indirect picture. For the diagnosis to be indisputable, direct confirmation of the presence of the pathogen or specific inflammation in the body is required. Reliability is based on two fundamental criteria:
- Bacteriological criterion. Implies the direct detection of Mycobacterium tuberculosis (MTB). Any biological fluids of the patient can serve as material for a successful search.
- Morphological criterion. Consists of pathomorphological (histological) confirmation that a specific tuberculous process is occurring in the affected tissues.
Principles of differential diagnosis
The diagnostic search is always built around the leading clinical syndrome and the specific localization of the lesion.
Lesions of the bronchopulmonary system
When the bronchopulmonary system and intrathoracic lymph nodes (ITLN) are involved, tuberculosis infection must be differentiated from a number of pathologies:
- Nonspecific (common) pneumonia.
- Congenital anomalies (malformations) of the respiratory system.
- Parasitic infestations presenting with lung damage.
- Lymphoproliferative diseases (hematological malignancies).
Extrapulmonary forms of tuberculosis
In extrapulmonary localizations, the vector of the search changes. Extrapulmonary forms require mandatory differentiation from the following conditions:
- Nonspecific inflammatory lesions of the respective organs and systems involved in the pathological process.
- Systemic vasculitis (this group of diseases must be strictly ruled out).
To remember the 100% diagnosis criteria: "Direct hit — BM" (Fluid Bacteriology + Tissue Morphology).
Class and exam questions
What is an absolutely reliable criterion for diagnosis?
Direct confirmation: bacteriological detection of mycobacteria in biological fluids or histological detection of specific inflammation in tissues.
In what cases is it preferable to use ultrasound?
Ultrasound examination is the method of choice when extrapulmonary lesions are suspected, such as in the abdominal organs, kidneys, or joints.
What is the differential diagnosis based on?
The differential search is always based on two factors: the leading clinical syndrome and the localization of the lesion.
What else to study on this topic
- Indications for studies using contrast enhancement
- Specifics of the morphological picture of the tuberculous process
- Differentiation of tuberculosis and systemic vasculitides
- Hematological malignancies in the differential diagnosis of bronchopulmonary lesions
- Imaging features of intrathoracic lymph nodes (ITLN)
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Other topics from the section «Chapter 12. Infectious and parasitic diseases»
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