How do you differentiate and treat gastritis versus gastroenteritis in a healthy adult?

Differentiating and Treating Gastritis vs Gastroenteritis in Healthy Adults

Gastritis is chronic inflammation of the stomach mucosa confirmed by histopathology, typically caused by H. pylori or autoimmunity, while gastroenteritis is acute inflammation of the stomach and intestines caused by infectious agents (predominantly viral), presenting with diarrhea, vomiting, and abdominal pain that resolves within days to a week. 1, 2

Key Clinical Distinctions

Gastritis Presentation

• Gastritis is a histological diagnosis requiring endoscopic biopsy confirmation, not a clinical syndrome 3
• Presents with dyspepsia (38%), bloating (25%), and upper abdominal discomfort rather than acute diarrheal illness 4
• Chronic course with persistent or recurrent symptoms over weeks to months 5
• Endoscopic features include pale mucosa, increased vascular visibility, thinning of gastric folds, and loss of rugae, though mucosa may appear normal in 20% of biopsy-proven cases 3, 4
• Diarrhea is uncommon unless concurrent enteritis is present 4

Gastroenteritis Presentation

• Acute onset with combination of nausea, vomiting, diarrhea, and abdominal pain 2, 6
• Norovirus (most common in adults) presents with 12-48 hour incubation, followed by vomiting, watery diarrhea, abdominal pain, myalgia, and low-grade fever, resolving in 12-72 hours 1, 2
• Rotavirus causes more severe symptoms lasting 4-7 days with prominent vomiting and fever 1
• Bacterial causes (Salmonella 11%, Campylobacter, Shigella) present with fever, bloody or mucoid diarrhea, and severe cramping 1

Diagnostic Approach

When to Investigate

Laboratory testing is NOT needed for mild gastroenteritis symptoms resolving within 7 days in stable patients 3, 1. However, investigation is warranted for:

• Symptoms persisting beyond 7 days 3, 1
• Visible blood in stool with fever 1
• Severe abdominal cramping or signs of systemic toxicity 1
• Recent antibiotic exposure (within 30 days) - test for C. difficile 3, 1
• Immunocompromised status 1
• Suspected outbreak situation 3

Diagnostic Testing for Gastroenteritis

• Multiplex PCR testing is now preferred over traditional stool cultures, offering 94% sensitivity for norovirus and faster results 1
• For suspected C. difficile (with recent antibiotic use), submit single diarrheal stool specimen for toxin assay; if negative and diarrhea persists, submit 1-2 additional specimens 3
• For colitis symptoms without antibiotic exposure, culture for Campylobacter, Salmonella, Shigella, and E. coli O157:H7 3
• Blood cultures indicated for suspected bacteremia with Salmonella or Yersinia 1

Diagnostic Testing for Gastritis

Gastritis diagnosis requires endoscopy with topographical biopsies from body and antrum/incisura placed in separately labeled jars 3. Additional workup includes:

• All patients with atrophic gastritis must be assessed for H. pylori infection using non-serological testing 3
• For autoimmune gastritis: check antiparietal cell antibodies, anti-intrinsic factor antibodies, vitamin B-12, and iron levels 3
• Fecal calprotectin helps distinguish inflammatory (gastritis/IBD) from non-inflammatory (gastroenteritis) causes when symptoms exceed 14 days 1

Treatment Algorithms

Gastroenteritis Management

Mild-to-Moderate Disease (No Red Flags):

• Oral rehydration with 8-10 large glasses of clear liquids daily 7, 2
• Eliminate lactose-containing products 7
• Antiemetic, antimotility, or antisecretory drugs for symptom control 2
• No antimicrobial therapy needed for viral causes 2

Severe Disease or Specific Indications:

• Nasogastric or intravenous hydration for those unable to tolerate oral intake 2
• C. difficile infection: Vancomycin 125 mg QID PO for 10 days or Fidaxomicin 200 mg BID PO for 10 days (preferred over metronidazole for severe disease) 3
• Salmonella bacteremia: Ceftriaxone plus ciprofloxacin combination initially, then de-escalate based on susceptibility 3
• Campylobacter, Shigella, or Yersinia with severe symptoms: antimicrobial therapy based on susceptibility 3
• Parasitic infections (Giardia, Cryptosporidium): specific antiparasitic therapy 3

Gastritis Management

H. pylori-positive gastritis:

• Eradicate H. pylori and confirm successful eradication using non-serological testing 3
• Treatment regimens follow standard H. pylori eradication protocols 3

Autoimmune gastritis:

• Treat vitamin B-12 and iron deficiencies 3
• Surveillance endoscopy every 3 years for advanced atrophic gastritis (extensive anatomic involvement and high histologic grade) 3
• Screen for type 1 gastric neuroendocrine tumors with endoscopy; remove small tumors endoscopically with surveillance every 1-2 years 3

Critical Pitfalls to Avoid

• Do not diagnose "gastritis" clinically without histopathologic confirmation - this is a common misuse of terminology 3, 5
• Do not order stool studies for mild gastroenteritis resolving within 7 days - this wastes resources and rarely changes management 3, 1
• Do not use metronidazole for severe C. difficile infection - vancomycin or fidaxomicin are superior 3
• Do not check H. pylori serology while patient is on PPIs - withdraw PPIs 10-14 days before testing (with caution and supervision) 3
• Do not assume normal-appearing gastric mucosa excludes gastritis - 20% of biopsy-proven cases have endoscopically normal mucosa 4

Post-Infectious Complications

Approximately 9-10% of patients with acute gastroenteritis develop post-infectious IBS, accounting for over 50% of all IBS cases 1, 2. Risk factors include bacterial infection, female sex, younger age, psychological distress, and severity of initial illness 1. C. difficile can cause post-infectious IBS in up to 25% of cases 1.