Gastrointestinal syndrome

Overview

Gastrointestinal syndrome, also known as gastrointestinal acute radiation syndrome (GI-ARS), is a severe clinical condition that occurs after exposure to high doses of ionizing radiation. It primarily affects the rapidly dividing cells of the gastrointestinal tract, leading to the breakdown of the intestinal lining, resulting in a cascade of symptoms including nausea, vomiting, diarrhea, dehydration, and sepsis. GI syndrome is one of the subtypes of acute radiation syndrome (ARS), and it typically manifests when individuals are exposed to radiation doses between 6 and 30 Gy (Gray units). The condition can be life-threatening without prompt medical intervention.

Causes

Gastrointestinal syndrome is caused by high-level exposure to ionizing radiation, such as during:

• Nuclear accidents or explosions

• Radiological terrorism or dirty bomb attacks

• Unshielded radiation sources in medical or industrial settings

• High-dose radiation therapy to the abdomen or pelvis (rare with modern safety standards)

The syndrome develops because radiation damages the stem cells in the crypts of the small intestine, impairing their ability to regenerate the intestinal epithelium. This leads to mucosal breakdown, fluid loss, and microbial translocation from the gut into the bloodstream.

Symptoms

Symptoms of gastrointestinal syndrome typically develop within hours to a few days after radiation exposure and may include:

• Severe nausea and vomiting (within 1–2 hours of exposure)

• Watery or bloody diarrhea

• Abdominal cramps and pain

• Loss of appetite

• Dehydration and electrolyte imbalance

• Weight loss

• Fever and signs of sepsis in advanced stages

• Fatigue and general weakness

The severity of symptoms depends on the radiation dose and the individual's overall health.

Diagnosis

Diagnosis of gastrointestinal syndrome involves a combination of exposure history, clinical presentation, and laboratory tests:

• Exposure history: Confirmed or suspected radiation exposure above 6 Gy

• Time to symptom onset: Rapid onset of vomiting and diarrhea is an early indicator

• Complete blood count (CBC): May show neutropenia and lymphopenia due to bone marrow suppression

• Electrolyte panels: Evaluate fluid and electrolyte imbalances

• Endoscopy or biopsy (rare): In some cases, to assess intestinal mucosal damage

• Biodosimetry: Laboratory methods to estimate radiation dose absorbed by the body

Treatment

There is no specific antidote for gastrointestinal syndrome, so treatment focuses on supportive care and mitigating complications:

• Fluid and electrolyte replacement: IV hydration to prevent dehydration and maintain electrolyte balance

• Antiemetics: To control nausea and vomiting

• Antidiarrheals: To reduce fluid loss from diarrhea

• Antibiotics: To prevent or treat bacterial infections due to intestinal barrier breakdown

• Nutritional support: May require parenteral nutrition in severe cases

• Growth factors: Such as granulocyte colony-stimulating factor (G-CSF) to support bone marrow recovery

• Stem cell transplantation: Considered in cases with concurrent hematopoietic syndrome

Early hospitalization and isolation may be necessary to manage the immunocompromised state of the patient.

Prognosis

The prognosis of gastrointestinal syndrome is generally poor, especially at higher radiation doses. Without aggressive supportive care, mortality is high due to complications such as dehydration, infection, and multiorgan failure. Survival chances decrease as radiation dose increases beyond 10 Gy. However, with early medical intervention, especially in patients exposed to lower doses within the GI-ARS range, some recovery is possible. Long-term survivors may suffer from chronic gastrointestinal issues due to radiation-induced fibrosis or scarring.