Gastritis

Inflammation of the gastric mucosa, which may be acute or chronic, and is histologically defined (distinct from "dyspepsia," which is a symptom complex that may or may not correlate with endoscopic/histologic gastritis).

Classified by:

• Acute gastritis: erosive/hemorrhagic (NSAIDs, alcohol, stress-related in critically ill) or non-erosive

• Chronic gastritis (Sydney system classification, by cause):

• H. pylori-associated (most common cause globally)

• Autoimmune gastritis (parietal cell antibodies, targets fundus/body, associated with pernicious anemia, B12 deficiency, increased gastric cancer/carcinoid risk)

• Chemical/reactive gastritis (NSAIDs, bile reflux, alcohol)

• Other: eosinophilic, lymphocytic, granulomatous (Crohn's, sarcoidosis), infectious (viral, fungal : immunocompromised)

• Often asymptomatic (many cases found incidentally on endoscopy)

• Epigastric pain/discomfort (burning or gnawing), often related to meals

• Nausea, vomiting, early satiety, bloating

• Hematemesis or melena if erosive/hemorrhagic gastritis with mucosal bleeding

• Autoimmune gastritis: may present with symptoms of B12 deficiency (fatigue, peripheral neuropathy: paresthesia, subacute combined degeneration of the cord, glossitis, cognitive changes) rather than GI symptoms

• Stress-related gastritis (critically ill/ICU patients): often asymptomatic until presenting with upper GI bleeding

• Red flag/alarm symptoms (warrant urgent endoscopy, exclude malignancy : especially age >55 with new symptoms): dysphagia, unintentional weight loss, persistent vomiting, GI bleeding (hematemesis/melena), iron-deficiency anemia, palpable epigastric mass, family history of upper GI cancer

H. pylori testing (first-line for most dyspepsia without alarm features ; "test and treat" strategy):

• Urea breath test or stool antigen test (non-invasive, preferred) : requires stopping PPI 2 weeks and antibiotics 4 weeks prior for accuracy

• Serology: detects past exposure, does not distinguish active infection, less useful for confirming eradication

• Endoscopic biopsy with rapid urease test (CLO test), histology, or culture: if endoscopy already indicated

• Upper GI endoscopy (OGD): indicated if alarm features present, age >55 with new dyspepsia, or symptoms refractory to initial treatment: allows direct visualization, biopsy (histology confirms gastritis type, excludes malignancy/dysplasia), and H. pylori testing

• Autoimmune gastritis workup (if suspected): parietal cell antibodies, intrinsic factor antibodies, B12 level, gastrin level (elevated due to loss of negative feedback), FBC (macrocytic anemia if B12 deficient)

• FBC: anemia if chronic blood loss or B12 deficiency

Differentials: peptic ulcer disease (may coexist), GERD, functional dyspepsia (symptoms without identifiable organic cause on endoscopy), gastric malignancy, biliary colic, pancreatitis, mesenteric ischemia (elderly, post-prandial pain).

H. pylori eradication (if positive) : standard triple therapy for 7–14 days:

• PPI (e.g., omeprazole 20mg bd) + amoxicillin 1g bd + clarithromycin 500mg bd

• Penicillin-allergic: substitute metronidazole 400mg bd for amoxicillin

• Rising clarithromycin resistance in many regions : consider quadruple therapy (bismuth-based: PPI + bismuth subsalicylate + metronidazole + tetracycline) as first-line where local resistance high, or as second-line after triple therapy failure

• Confirm eradication with urea breath test or stool antigen ≥4 weeks after completing treatment (and ≥2 weeks off PPI)

Symptomatic/acid suppression:

• PPI (omeprazole 20-40mg od, or equivalent) : first-line, 4–8 week course, taper/reassess

• H2 receptor antagonists (famotidine) : alternative if PPI not tolerated/available

• Antacids for symptomatic relief (short-term)

Removal of causative agents:

• Discontinue/reduce NSAIDs where possible; if ongoing NSAID need (e.g., for arthritis), co-prescribe PPI for gastroprotection, consider COX-2 selective agent

• Alcohol cessation/reduction counseling

• Address bile reflux if chemical gastritis from this cause (prokinetics, ursodeoxycholic acid : limited evidence, surgical options in severe refractory cases)

Stress-related gastritis (ICU/critically ill patients):

• Prophylactic PPI or H2RA in high-risk patients (mechanical ventilation >48h, coagulopathy, high-dose steroids, severe burns/trauma) : reduces stress ulcer bleeding risk

Autoimmune gastritis:

• Lifelong B12 replacement: IM hydroxocobalamin 1mg alternate days for 2 weeks, then 1mg every 2–3 months (lifelong) : cannot rely on oral replacement if intrinsic factor deficient

• Iron deficiency correction if present (achlorhydria impairs iron absorption)

• Surveillance endoscopy: increased risk of gastric adenocarcinoma and type 1 gastric carcinoid, periodic endoscopic surveillance recommended (interval per local guidelines, generally every 3-5 years)

Erosive/hemorrhagic gastritis with active bleeding:

• Resuscitation as per upper GI bleed protocol, IV PPI (high-dose, e.g., omeprazole 80mg bolus then infusion), endoscopic hemostasis if actively bleeding lesion identified, correct coagulopathy

Lifestyle advice: smaller frequent meals, avoid triggers (spicy food, alcohol, caffeine : evidence modest but commonly advised), smoking cessation, weight management if overweight (reduces intra-abdominal pressure-related symptoms).

Referral/follow-up: repeat endoscopy if alarm features, non-response to treatment, or to confirm healing of erosive disease; gastroenterology referral for autoimmune gastritis surveillance, refractory H. pylori infection (multiple eradication failures), or diagnostic uncertainty.