Gastritis

• Patho/Etiology
  • Acute (Erosive) Gastritis: Sudden inflammation of the gastric mucosa, often with neutrophilic infiltration.
    • Causes: NSAIDs (inhibit prostaglandins, reducing mucosal protection), alcohol, smoking, severe stress (e.g., burns [Curling’s ulcer], brain injury [Cushing’s ulcer]), and initial H. pylori infection.
  • Chronic (Non-Erosive) Gastritis: Long-term inflammation leading to mucosal atrophy and metaplasia, primarily with mononuclear cell infiltration (lymphocytes, plasma cells).
    • Type A (Autoimmune): Affects the body and fundus. Autoantibodies attack parietal cells (leading to ↓ HCl and ↓ intrinsic factor) and/or intrinsic factor itself. This results in achlorhydria and pernicious anemia.
    • Type B (Bacterial): Most common type, caused by H. pylori. Typically starts in the antrum and can spread. H. pylori produces urease, which creates an alkaline environment to survive gastric acid.
• Clinical Presentation
  • Acute: Often presents with epigastric pain, N/V, and anorexia. In severe cases, it can cause hematemesis or melena (erosive gastropathy).
  • Chronic: Can be asymptomatic or cause vague dyspepsia and abdominal discomfort.
    • Autoimmune: Patients may show symptoms of pernicious anemia (megaloblastic anemia) and neurologic deficits due to B₁₂ deficiency (e.g., peripheral neuropathy). May also present with iron deficiency anemia.
• Diagnosis
  • Endoscopy with biopsy: Gold standard to visualize inflammation, erosions, and atrophy, and to obtain tissue for histology.
  • H. pylori testing: Urea breath test or stool antigen test for active infection. Serology is less useful for confirming active infection.
  • Labs:
    • Autoimmune gastritis: Look for anti-parietal cell and anti-intrinsic factor antibodies, ↓ Vitamin B₁₂ levels, and ↑ gastrin (due to achlorhydria).
    • Anemia: CBC may show microcytic anemia (Fe deficiency) or macrocytic anemia (B₁₂ deficiency).
• DDx (Differential Diagnosis)
  • Peptic Ulcer Disease (PUD): More localized, deeper mucosal defect. Duodenal ulcer pain often improves with food, while gastric ulcer pain worsens with food.
  • GERD: Characterized by retrosternal burning (heartburn) and regurgitation, worse when supine.
  • MI: Must be ruled out, especially with epigastric pain radiating to the arm/jaw, associated with SOB, and EKG changes.
  • Pancreatitis: Epigastric pain radiating to the back, with elevated lipase/amylase.
  • Gastric Cancer: Consider in patients with alarm symptoms (weight loss, anemia, dysphagia), especially in chronic gastritis.
• Management/Treatment
  • General: Remove offending agents like NSAIDs and alcohol.
  • Acid Suppression: PPIs (e.g., omeprazole) or H₂ blockers.
  • H. pylori Eradication: Triple therapy (PPI + clarithromycin + amoxicillin/metronidazole) or Quadruple therapy (PPI + bismuth + metronidazole + tetracycline).
  • Autoimmune Gastritis: Lifelong Vitamin B₁₂ supplementation (parenteral).
• Key Associations/Complications
  • PUD: Chronic gastritis is a major risk factor.
  • Gastric Adenocarcinoma: Increased risk with both autoimmune and H. pylori-associated chronic atrophic gastritis due to intestinal metaplasia.
  • MALT Lymphoma: Strongly associated with chronic H. pylori infection.
  • Neuroendocrine Tumors (Carcinoid): A risk in autoimmune gastritis due to G-cell hyperplasia from chronic achlorhydria and elevated gastrin.