Acute Radiation Syndrome

Hematological manifestations: anemia syndrome

Radiation exposure in the range of 1 to 6 Gy primarily affects the most radiosensitive tissue of the body — the red bone marrow, whose cells are characterized by a high proliferation rate.

The manifestation of anemia syndrome is not instantaneous: the concentration of erythrocytes in peripheral blood drops sharply a few days after exposure. This time is required for the complete depletion of the pool of already circulating mature cells. Progressive severe anemia inevitably leads to a pronounced deficiency of oxygen (O₂) in all body tissues.

Secondary immunodeficiency and septic syndrome

In addition to the erythroid lineage, radiation has a detrimental effect on lymphoid tissue. In the lymph nodes, the processes of proliferation and differentiation of lymphocytes and macrophages are blocked. Their normal interaction, necessary for the generation of antibody-forming cells and the activation of immune effector links, is disrupted.

Peripheral blood shows leukopenia and thrombocytopenia. Due to a critical decrease in leukocytes and suppression of lymphocyte proliferation, secondary immunodeficiency develops.

Against this background, the resident opportunistic flora inhabiting the mucous membranes of the respiratory and gastrointestinal tracts becomes activated and causes severe infectious complications, grouped under the concept of septic syndrome.

Note on cytopenia diagnostics: In the differential diagnosis of conditions accompanied by a decreased platelet count, the morphological criterion of choice is platelet size. Forms include microthrombocytopenia (e.g., Wiskott–Aldrich syndrome), normocytopenia (TAR syndrome, congenital amegakaryocytic thrombocytopenia), and macrothrombocytopenia (Bernard–Soulier syndrome, gray platelet syndrome).

Gastrointestinal syndrome

When exposed to a dose above 6 Gy, damage to the digestive system comes to the forefront. The mechanism of development is associated with the direct death of gastric and intestinal epithelial cells.

Key manifestations:

• Profuse diarrhea.
• Formation of necrosis and ulcers on the gastrointestinal mucosa (including the oral cavity).
• Zones of radiation necrosis lose their barrier function and become the entry gates for massive infection.
• The combination of necrotic intestinal damage and a sharp suppression of the immune response (described above) leads to the rapid development of peritonitis and systemic sepsis.

Cerebral syndrome

Extremely high doses of radiation (above 80 Gy) cause fatal damage to the central nervous system. Although neurons of the brain and spinal cord do not divide, they have high oxygenation, making them vulnerable at such doses.

Symptoms develop rapidly, within several hours after exposure:

1. Intractable severe headache and vomiting.
2. Pronounced motor incoordination.
3. Impairment of cognitive processes.
4. Seizures and paralysis.
5. Progressive depression of consciousness transitioning into coma.

The prognosis for this form is utterly unfavorable: the patient's death occurs within 1–2 days.

Class and exam questions

What else to study on this topic

• Diagnostic imaging of nephrocalcinosis (ultrasound, CT, and lesion localization)
• Classification and imaging semiotics of cystic kidney diseases (including the Bosniak scale)
• Diagnostics of urolithiasis and renal colic (the role of dual-energy CT)
• Radiological manifestations of cystic fibrosis and pancreatic pathologies in children
• PET-scintigraphy with 18F-fluorodopa in congenital hyperinsulinism

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.