Phlegmonous Gastritis

Phlegmonous gastritis is a rare, acute, suppurative bacterial infection of the gastric submucosa that can spread to the muscularis and serosa. It is a surgical emergency with a mortality of 30% to 60%. Emphysematous gastritis is the gas forming variant.

Fewer than 1,000 cases have been reported. It is commoner in men aged 40 to 60 years.

Organisms are streptococci (alpha- and beta haemolytic) in over half of cases, Staphylococcus aureus, Escherichia coli, Klebsiella, Pseudomonas, Proteus, Haemophilus influenzae and anaerobes. Clostridium species cause emphysematous disease.

Risk factors are alcohol use disorder, immunosuppression, AIDS, chemotherapy, achlorhydria (including long term acid suppression), gastric ulcer or cancer, recent endoscopic interventions (injection, polypectomy, mucosal resection), uraemia and gastric surgery.

Pathophysiology.

Bacteria breach the mucosal barrier and multiply in the loose submucosa, causing purulent inflammation, thrombosis of vessels and necrosis. Spread leads to abscess, perforation, peritonitis and septicaemia.

Severe epigastric pain, fever, rigors, vomiting (occasionally purulent), peritonism and shock. The history may include a recent endoscopic procedure.

Red flags.

• Shock or sepsis.
• Peritonitis.
• Purulent vomit.
• Intramural gas.

CT shows marked gastric wall thickening with low attenuation submucosa, mucosal enhancement, intramural gas, and perigastric fat stranding or abscess. Endoscopy (with minimal insufflation because of perforation risk) shows thickened, oedematous, erythematous mucosa with purulent exudate. Blood cultures, full blood count, C-reactive protein and lactate are sent. Culture gastric aspirate or tissue.

Differential diagnosis.

• Gastric ischaemia.
• Gastric cancer or lymphoma.
• Acute pancreatitis.
• Perforated ulcer.
• Corrosive injury.
• Gastroenteritis.

Give intravenous antibiotics at once, resuscitate and involve surgeons. Operate for necrosis, perforation or abscess (drainage or gastrectomy). Endoscopic or percutaneous drainage can treat localised collections in stable patients.

• Piperacillin-tazobactam: 4.5 g IV every 6 hours; at least 14 days, and until imaging and inflammatory markers settle; maximum 18 g daily; monitor renal function, blood counts and cultures; reduce for creatinine clearance under 40 mL/min.
• Vancomycin (added when meticillin resistant staphylococci are likely): 25 to 30 mg/kg IV loading dose, then 15 to 20 mg/kg every 8 to 12 hours; for the duration of treatment; target area under the curve 400 to 600; monitor renal function and levels; extend the interval in renal impairment.
• Meropenem (alternative for resistant Gram negative organisms): 1 g IV every 8 hours; maximum 6 g daily; monitor renal function and seizures; reduce for creatinine clearance under 50 mL/min.
• Pantoprazole: 40 mg IV once daily while nil by mouth; maximum 80 mg daily; monitor magnesium; reduce to 20 mg daily in severe hepatic impairment.

Provide nutritional support, with parenteral nutrition if enteral feeding is not feasible.

Monitoring. Vital signs, lactate, inflammatory markers daily, repeat CT at 5 to 7 days or with deterioration.

Referral and escalation. Emergency upper gastrointestinal surgery, infectious diseases and critical care.