Acute Gastritis

Acute inflammation of the gastric mucosa, ranging from mild epithelial injury to erosions and bleeding, usually self-limiting over days when the cause is removed.

• Causes: non-steroidal anti-inflammatory drugs and aspirin, alcohol, acute Helicobacter pylori infection, severe physiological stress (critical illness, burns, major surgery, trauma; stress-related mucosal disease), bile reflux, viral infection (cytomegalovirus, herpes simplex), bacterial infection (phlegmonous gastritis, rare), caustic or corrosive ingestion, radiation, iron or potassium tablets, chemotherapy, Crohn disease and food poisoning.
• Frequency: up to a quarter of people on regular NSAIDs have endoscopic erosions; stress-related mucosal bleeding occurs in about 1 to 4% of intensive care patients without prophylaxis.
• Mechanism: damage to the mucus and bicarbonate barrier and prostaglandin depletion (NSAIDs), direct toxicity, ischaemia (stress), and an inflammatory response to infection, with back-diffusion of acid.

Epigastric pain or discomfort, nausea, vomiting, anorexia, bloating, belching, early satiety; often asymptomatic.

• Erosive disease: haematemesis (coffee grounds or fresh blood), melaena, iron deficiency anaemia; in critically ill patients bleeding may be the first sign.
• Examination: mild epigastric tenderness, no peritonism.
• Differential diagnosis: peptic ulcer disease, non-ulcer dyspepsia, gastro-oesophageal reflux, gastric cancer, biliary colic, pancreatitis, gastroenteritis, myocardial infarction (inferior), gastroparesis, medication effects, eosinophilic gastroenteritis.
• Complications: gastrointestinal bleeding (haematemesis and melaena), iron deficiency anaemia, gastric outlet obstruction (rare), perforation (rare), progression to chronic gastritis and ulcer, and, in corrosive injury, necrosis and stricture.

Clinical diagnosis in most; investigations are used for alarm features: age 55 years or more with new dyspepsia, weight loss, dysphagia, persistent vomiting, anaemia, gastrointestinal bleeding, palpable mass, family history of gastric cancer.

• Oesophagogastroduodenoscopy: erythema, erosions, haemorrhage, with biopsies (antrum, angularis and body, five biopsies) for histology and H. pylori; within 24 hours for bleeding.
• Helicobacter pylori testing: urea breath test or stool antigen (stop proton pump inhibitors for 2 weeks and antibiotics for 4 weeks before testing); histology and rapid urease test during endoscopy; serology only for diagnosis in patients who cannot stop acid suppression (it cannot confirm eradication).
• Blood tests: full blood count, urea, creatinine, electrolytes, liver tests, lipase when pain is severe, group and screen if bleeding; ECG and troponin in older patients with epigastric pain.
• Cytomegalovirus and other infections by histology and polymerase chain reaction in immunosuppressed patients.

Remove the cause: stop NSAIDs and aspirin where possible (if aspirin is essential for cardiovascular protection, continue 75 mg daily with a proton pump inhibitor), stop alcohol, avoid smoking and irritant foods, and review iron or potassium tablets.

• Acid suppression:
  • Omeprazole 20 mg once daily (or pantoprazole 40 mg daily, lansoprazole 30 mg daily) for 2 to 4 weeks, taken 30 minutes before breakfast; 40 mg daily for erosions or when symptoms are severe.
  • Famotidine 20 mg twice daily (10 mg twice daily if creatinine clearance is less than 50 mL/min) as an alternative.
• Symptom relief:
  • Alginate-antacid (sodium alginate and potassium bicarbonate 10 to 20 mL after meals and at bedtime) as needed.
  • Antiemetic ondansetron 4 mg IV or 8 mg orally every 8 hours, or metoclopramide 10 mg three times daily orally or IV (maximum 5 days).
  • Oral rehydration solution, with IV fluids if not tolerating oral intake (sodium chloride 0.9% with potassium 20 to 40 mmol/L).
• Helicobacter pylori eradication when positive, for 14 days:
  • Omeprazole 20 mg twice daily with amoxicillin 1 g twice daily and clarithromycin 500 mg twice daily (use only where clarithromycin resistance is less than 15%).
  • Bismuth quadruple therapy (preferred where resistance is high): omeprazole 20 mg twice daily, bismuth subsalicylate 524 mg four times daily (or bismuth subcitrate 120 mg four times daily), tetracycline 500 mg four times daily, and metronidazole 500 mg three to four times daily.
  • Penicillin allergy: omeprazole 20 mg twice daily, clarithromycin 500 mg twice daily and metronidazole 400 to 500 mg twice daily, or omeprazole 20 mg twice daily, bismuth subsalicylate 524 mg four times daily, tetracycline 500 mg four times daily and metronidazole 500 mg three to four times daily.
  • Test of cure by urea breath test or stool antigen at least 4 weeks after antibiotics and 2 weeks off the proton pump inhibitor.
• Bleeding:
  • Resuscitation (two large-bore cannulae, crystalloid, transfuse to haemoglobin of 70 g/L or more, or 80 g/L or more with cardiovascular disease).
  • Intravenous omeprazole 80 mg bolus then 8 mg/hour for 72 hours, or 40 mg twice daily.
  • Endoscopy within 24 hours with endoscopic therapy (adrenaline injection with clip or thermal coagulation) for active bleeding or visible vessel.
  • Tranexamic acid is not helpful.
• Stress-related mucosal disease prophylaxis (intensive care): pantoprazole 40 mg IV daily, or famotidine 20 mg IV twice daily. Give it for patients with mechanical ventilation for more than 48 hours, coagulopathy (platelets less than 50 x 10^9/L or INR more than 1.5), shock, or renal failure. Stop when risk factors resolve; enteral feeding also helps.
• Corrosive injury: nil by mouth, endoscopy within 12 to 24 hours, IV fluids, omeprazole 40 mg IV twice daily, no induced vomiting or neutralisation, surgery for perforation or necrosis.
• Gastroprotection for patients who must continue NSAIDs: omeprazole 20 mg daily; use the lowest NSAID dose, or a cyclo-oxygenase 2 inhibitor (celecoxib 100 to 200 mg twice daily) plus omeprazole in high-risk patients.
• Special groups:
  • Children: omeprazole 0.7 to 1 mg/kg once daily (maximum 20 mg), oral rehydration, treat H. pylori with weight-based amoxicillin 25 mg/kg twice daily and clarithromycin 7.5 mg/kg twice daily with omeprazole 1 mg/kg twice daily for 14 days.
  • Pregnancy: antacids and alginates first; famotidine 20 mg twice daily or omeprazole 20 mg daily if needed; avoid bismuth, tetracycline and clarithromycin, and defer H. pylori eradication until after delivery.
  • Elderly: stop NSAIDs where possible, higher bleeding risk, low threshold for endoscopy.
  • Renal impairment: famotidine dose reduction, avoid magnesium and aluminium antacids in severe disease.
  • Immunosuppression: test for cytomegalovirus and fungi; ganciclovir 5 mg/kg IV every 12 hours for 2 to 3 weeks for cytomegalovirus gastritis.
• Red flags: haematemesis or melaena, persistent vomiting, dysphagia, weight loss, anaemia, age 55 years or more with new symptoms, severe pain with rigidity (perforation), no improvement in 2 weeks.
• Follow-up: review at 2 to 4 weeks; repeat endoscopy for gastric ulcers or alarm features after 6 to 8 weeks; test of cure for H. pylori; long-term proton pump inhibitor only for continuing NSAID or aspirin use; check haemoglobin after bleeding.