What is the link between influenza A (flu A) and pancreatitis?

The Link Between Influenza A and Pancreatitis

Influenza A virus can directly infect pancreatic cells, causing pancreatitis that may lead to significant complications including hyperglycemia and diabetes in some cases. 1

Pathophysiological Mechanism

• Influenza A viruses can infect pancreatic tissue, with viral nucleoprotein detectable in acinar tissue and beta cells, leading to pancreatic inflammation 1
• The infection triggers a significant inflammatory cytokine response including increased levels of MIG/CXCL9, IP-10/CXCL10, RANTES/CCL5, MIP1b/CCL4, Groa/CXCL1, IL-8/CXCL8, TNF-α, and IL-6 1
• This inflammatory cascade can cause severe fibrosis and disruption of pancreatic structure, potentially resulting in both exocrine and endocrine dysfunction 1

Clinical Presentation and Diagnosis

• Patients with influenza A-associated pancreatitis typically present with:

  • Abdominal pain characteristic of acute pancreatitis 2
  • Elevated pancreatic enzymes (lipase, amylase) at least 3 times the upper limit of normal 2
  • Concurrent flu-like symptoms 3

• Laboratory markers that should be evaluated include:

  • Lipase and amylase levels 4
  • White blood cell count 4
  • C-reactive protein 4
  • Procalcitonin (PCT) - considered the most sensitive laboratory test for detection of pancreatic infection 4

• Imaging studies that can confirm pancreatitis include:

  • Ultrasound 4
  • CT with IV contrast 4
  • MRI 4
  • Endoscopic ultrasound (EUS) 4

Clinical Significance and Complications

• In animal models, influenza A infection of the pancreas has been shown to cause:

  • Hyperlipasemia in over 50% of subjects 1
  • Progression to hyperglycemia and diabetes in some cases 1
  • Severe fibrosis and disruption of pancreatic structure 1

• People with diabetes are at approximately twofold higher risk of developing acute pancreatitis, suggesting a bidirectional relationship 4

Management Considerations

• Management depends on the severity of pancreatitis:

1. For mild acute pancreatitis:

   • Regular diet with advancement as tolerated 4
   • Oral pain medications 4
   • Routine vital signs monitoring 4

2. For moderately severe acute pancreatitis:

   • Enteral nutrition (oral, nasogastric, or nasojejunal) 4
   • IV pain medications 4
   • IV fluids to maintain hydration 4
   • Monitoring of hematocrit, BUN, and creatinine 4
   • Continuous vital signs monitoring 4

3. For severe acute pancreatitis:

   • Enteral nutrition with parenteral nutrition if not tolerated 4
   • IV pain medications 4
   • Early fluid resuscitation 4
   • Mechanical ventilation if needed 4

Important Considerations

• Routine prophylactic antibiotics are not recommended for acute pancreatitis 4
• Antibiotics should only be administered to treat infected acute pancreatitis 4
• For suspected infected pancreatitis, diagnostic approaches include:
  • Procalcitonin measurement 4
  • CT- or EUS-guided fine-needle aspiration for Gram stain and culture 4

Rare Cases and Differential Diagnosis

• While influenza A has been documented to cause pancreatitis, cases of influenza B causing pancreatitis are extremely rare and should be approached with caution 5, 6
• Some cases of pancreatitis may present with normal pancreatic enzymes, making diagnosis challenging 6
• Influenza-associated pancreatitis has been reported in both adults and children 2, 3

Caution in Establishing Causality

• Before attributing pancreatitis to influenza infection, other common causes should be ruled out, including:

  • Gallstones 5
  • Alcohol consumption 5
  • Other infectious agents 2
  • Metabolic disorders 2
  • Trauma 2

• False positive PCR results for influenza have been reported, highlighting the need for careful confirmation before establishing novel infectious etiologies for pancreatitis 5