Morphological database: the role of histology
Histological examination ensures accurate morphological verification of pathologies. This serves as the foundation for the differential diagnosis of diffuse lesions and various oncological processes. The analysis utilizes biopsy or surgical material obtained via puncture ("blind"), laparoscopy, or ultrasound guidance.
The obtained tissues and cells are analyzed using a range of methods:
- Staining (e.g., hematoxylin and eosin).
- Immunohistochemistry (IHC) using monoclonal antibodies.
- Molecular genetic tests and electron microscopy.
Important: the turnaround time for histological analysis must not exceed 15 working days, and specialized medical care for the patient must begin no later than 14 calendar days after the confirmation (verification) of the diagnosis.
Differential search in infectious processes
When examining a patient with an infection, it is important to be able to distinguish between clinically similar nosologies. For example, in suspected scarlet fever caused by Streptococcus pyogenes, differential diagnosis must be performed against other acute viral and bacterial diseases. Comparison criteria include the presence of a characteristic rash (exanthema), inflammation of the palatine tonsils (tonsillitis), and enlargement of the lymph nodes (lymphadenopathia).
In pulmonology, a classic task is the differential diagnosis of pulmonary tuberculosis from other granulomatous or parasitic lesions. If baseline triple diagnostics (sputum microscopy, culture, and molecular genetic methods) yield negative results, the diagnostic search is expanded:
- Imaging methods: chest CT, two-view radiography, and tomosynthesis are ordered to determine the localization, form, and activity of the inflammation.
- Tuberculin skin testing: skin tests help rule out or confirm the specific nature of the granulomatous process.
- Bronchoalveolar lavage (BAL) fluid analysis: the cytogram of a healthy non-smoker shows a predominance of alveolar macrophages (up to 90%) with a minimal neutrophil count (1–2%). In sarcoidosis, lymphocytes begin to significantly predominate over neutrophils. In infections (including in HIV-infected patients), pneumocystis or fungi can be detected in the lavage fluid.
Determining the causes of impaired consciousness and coma
The examination of a patient with altered consciousness requires simultaneous evaluation and life support (correction of vascular collapse, securing the airway). Neurological status assessment is aimed at the differential diagnosis of the causes of coma. Broadly, it is divided into two types:
- Metabolic — arises due to profound brain dysfunction secondary to toxic or systemic metabolic disturbances.
- Destructive — the consequence of a widespread or localized (focal) organic lesion of brain tissue. In this case, neurological status helps suggest the topography (localization) of the lesion.
| Diagnostic focus | Applied methods |
|---|---|
| Baseline screening | CBC, urinalysis, ECG, chest radiography, blood biochemistry (glucose, creatinine, urea, electrolytes, liver function tests, plasma osmolality). |
| Ruling out intoxication | Toxicological urine and blood screening for barbiturates, tranquilizers, ethanol. |
| Suspected neuroinfection | Lumbar puncture with mandatory cerebrospinal fluid (CSF) analysis. |
| Suspected trauma | CT or radiography of the cervical spine, abdominal examination (to rule out internal hemorrhage). |
| Suspected brain injury | Brain CT or MRI. Alternatives: EEG, echoencephalography, skull radiography. |
The causes of impaired consciousness in differential diagnosis are easy to remember using the rule of three categories: Metabolic shifts, Toxic exposures, Organic brain lesions (MTO).
Class and exam questions
How does a bronchoalveolar lavage cytogram aid in differential diagnosis?
Normally, macrophages predominate in lavage fluid. In sarcoidosis, lymphocytes outnumber neutrophils, and in specific infections, the pathogens themselves are identified (e.g., fungi or pneumocystis).
What pathologies are differentiated from the clinical presentation of scarlet fever?
Scarlet fever is differentiated from other acute bacterial and viral infections that also present with a skin rash, tonsillitis, and lymphadenopathy.
What is the main difference between destructive and metabolic coma?
Destructive coma is associated with focal or widespread organic damage to brain structures. The metabolic form occurs due to neuronal dysfunction caused by toxins or severe metabolic disorders.
What else to study on this topic
- Quality criteria for medical care and tuberculosis diagnostic algorithms.
- Pathogenic mechanisms and epidemiology of Streptococcus pyogenes.
- Clinical presentation of deep (profound) coma: areflexia and diffuse hypotonia.
- Priority tasks during the initial examination of an unconscious patient.
- Historical contributions of scientists to the development of tissue diagnostics and cytology.
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