What tests and procedures are used to diagnose acute gastritis?

Diagnostic Approach to Acute Gastritis

Upper endoscopy with targeted biopsies is the gold standard for diagnosing acute gastritis, with additional testing for H. pylori infection using rapid urease test, histology, or culture from the biopsies. 1, 2

Primary Diagnostic Tests

1. Upper Endoscopy with Biopsies

• Endoscopy allows direct visualization of gastric mucosa to identify:

  • Mucosal inflammation, erythema, erosions
  • Pale appearance of gastric mucosa
  • Increased visibility of vasculature due to mucosal thinning
  • Loss of gastric folds
  • Light blue crests and white opaque fields (if intestinal metaplasia present) 1

• Biopsy Protocol:

  • Obtain biopsies from both antrum and body/corpus (placed in separate containers)
  • Target any visible abnormal areas
  • Topographical biopsies help determine anatomic extent and histologic severity 1

2. H. pylori Testing

H. pylori is a common cause of gastritis, requiring specific testing:

• Invasive tests (during endoscopy):

  • Rapid urease test (RUT): 77-95% sensitivity, 95% specificity 1, 2
  • Histology with H&E stain or immunohistochemistry: Highly sensitive and specific 3
  • Culture: Allows antibiotic susceptibility testing 1

• Non-invasive tests (if endoscopy not performed):

  • Urea breath test (UBT): 95% sensitivity and specificity 2
  • Stool antigen test (SAT): 88-90% sensitivity, 91-100% specificity 2
  • Serology (ELISA): 90% sensitivity, 95% specificity (not recommended for follow-up) 2

Additional Tests to Consider

1. Laboratory Studies

• Complete blood count (CBC): To assess for anemia or infection 1
• Serum chemistries: To evaluate overall health status 1
• Iron studies and vitamin B12 levels: Particularly in chronic gastritis 1
• For suspected autoimmune gastritis:
  • Anti-parietal cell antibodies
  • Anti-intrinsic factor antibodies 1

2. Imaging Studies (if complications suspected)

• CT abdomen with IV and neutral oral contrast: If perforation or severe disease suspected 1
• Upper GI series (double-contrast): Can identify gastritis features including enlarged areae gastricae, thickened gastric folds, erosions, or ulcers 1

Special Considerations

For Autoimmune Gastritis

• Check anti-parietal cell and anti-intrinsic factor antibodies
• Evaluate for anemia and vitamin B12/iron deficiencies
• Consider screening for other autoimmune conditions (thyroid disease) 1

For H. pylori Gastritis

• Confirm eradication after treatment using UBT or SAT (at least 4 weeks post-treatment)
• Avoid serology for confirmation of cure 2

Diagnostic Algorithm

1. Initial presentation with epigastric pain, nausea, vomiting, bloating:

   • If age >45 or alarm symptoms (hematemesis, melena, weight loss, dysphagia, anemia): Proceed directly to endoscopy
   • If age <45 without alarm symptoms: Consider non-invasive H. pylori testing first

2. During endoscopy:

   • Obtain biopsies from antrum and body (separate containers)
   • Perform rapid urease test
   • Target any visible lesions for additional biopsies

3. Histopathology assessment:

   • Evaluate for inflammation, activity, atrophy, intestinal metaplasia
   • Special stains or immunohistochemistry for H. pylori if needed 3

Common Pitfalls to Avoid

• Failing to obtain biopsies from both antrum and body, which can miss corpus-predominant patterns of gastritis 1
• Not testing for H. pylori in all patients with gastritis 2
• Using serology to confirm H. pylori eradication (antibodies remain elevated for months) 2
• Missing autoimmune gastritis by not considering appropriate antibody testing 1
• Inadequate biopsy sampling that may miss focal lesions or multifocal atrophic gastritis 4

Remember that while endoscopy with biopsies remains the gold standard for diagnosing acute gastritis, the specific testing approach may need to be tailored based on clinical presentation, age, and presence of alarm symptoms.