Gastritis e.c. H. pylori

01Pathophysiology

Helicobacter pylori is a gram-negative, spiral-shaped bacterium uniquely adapted to survive in the harsh acidic environment of the stomach. The key survival mechanism is its production of urease, an enzyme that hydrolyzes urea into ammonia (${\text{NH}}_3\backslash text\{NH\}\_3$) and carbon dioxide (${\text{CO}}_2\backslash text\{CO\}\_2$). The ammonia creates a local alkaline buffer around the organism, neutralizing gastric acid and allowing colonization of the mucus layer overlying the gastric epithelium. This urease activity is also the biochemical basis of several diagnostic tests, including the urea breath test and the rapid urease test on biopsy specimens.

Once established, H. pylori adheres to gastric epithelial cells using adhesins such as BabA and SabA. The organism then deploys virulence factors that directly damage the mucosa. CagA (cytotoxin-associated gene A) is injected into host cells via a type IV secretion system, disrupting intracellular signaling, promoting inflammation, and increasing the risk of malignant transformation. VacA (vacuolating cytotoxin A) induces epithelial cell vacuolation and apoptosis, weakens tight junctions, and suppresses local immune responses. Together, these factors trigger a robust inflammatory infiltrate dominated by neutrophils and lymphocytes, which defines chronic active gastritis on histology.

The anatomic distribution of inflammation determines the clinical consequence, and this is a heavily tested concept. Antral-predominant gastritis destroys somatostatin-producing D cells in the antrum, removing the negative feedback on gastrin release. The result is hypergastrinemia, increased parietal cell acid output, and a predisposition to duodenal ulcers. In contrast, corpus-predominant gastritis (or pangastritis) damages the acid-producing parietal cells themselves, leading to hypochlorhydria, progressive gastric atrophy, and intestinal metaplasia. This pattern carries increased risk for gastric adenocarcinoma and gastric MALT lymphoma. Understanding this divergence explains why duodenal ulcers are associated with high acid states while gastric ulcers and gastric cancer are associated with low acid states, both driven by the same organism.

The link to MALT lymphoma deserves emphasis. Chronic antigenic stimulation by H. pylori drives clonal expansion of marginal zone B cells in the gastric mucosa. In early-stage, low-grade MALT lymphoma, eradication of H. pylori alone can lead to complete tumor regression, making it one of the few cancers where antibiotic therapy is the first-line treatment.

02Classification and Clinical Manifestation

03Diagnostic Workup

The diagnostic approach depends on whether the patient has alarm symptoms or is below 60 years of age.

For younger patients without alarm features (no unintended weight loss, no dysphagia, no gastrointestinal bleeding, no persistent vomiting, no family history of gastric cancer), the recommended strategy is "test and treat" without endoscopy. The urea breath test or stool antigen test is the best initial test. Both detect active infection with high sensitivity and high specificity. If positive, empiric eradication therapy is started. If negative, an alternative diagnosis such as functional dyspepsia should be considered.

For patients with alarm symptoms or those aged 60 and older, upper endoscopy with biopsy is indicated. This is the most accurate test and allows direct visualization of the mucosa, histologic confirmation of gastritis, detection of ulceration, and exclusion of malignancy. During endoscopy, a rapid urease test can provide results within hours by placing the biopsy specimen on a urea-containing gel. A positive color change confirms active H. pylori colonization.

Serology detects IgG antibodies against H. pylori and is useful for population-level screening, but it is a poor choice for confirming active disease or for assessing eradication. Antibodies can persist for months to years after successful treatment, making serology unreliable as a test of cure.

A critical testing rule: proton pump inhibitors must be discontinued at least 2 weeks and antibiotics at least 4 weeks before performing UBT, stool antigen, or rapid urease testing. These medications suppress bacterial load and urease activity, leading to false-negative results. This is one of the most commonly tested pitfalls.

04Management and Treatment

Acute treatment begins with selecting the appropriate eradication regimen. In regions where clarithromycin resistance remains below 15%, 14-day triple therapy with a PPI, clarithromycin, and amoxicillin is standard. The PPI raises intragastric pH, which improves antibiotic bioavailability and bacterial susceptibility. In patients with a true penicillin allergy, amoxicillin is replaced by metronidazole.

Where clarithromycin resistance exceeds 15%, or when the patient has had prior macrolide exposure for any reason, bismuth quadruple therapy is preferred. Bismuth has direct antimicrobial and cytoprotective properties and works synergistically with metronidazole and tetracycline. This regimen is also the standard second-line rescue after failure of clarithromycin-based triple therapy.

Confirmation of eradication is mandatory. The test of cure should be performed no sooner than 4 weeks after completing all antibiotics and at least 2 weeks after stopping PPIs. The preferred modalities are the urea breath test or stool antigen test. Serology must never be used for this purpose because antibody titers decline slowly and unreliably.

If eradication fails after two attempts, culture with antibiotic sensitivity testing is recommended to guide a tailored salvage regimen. Referral to a gastroenterologist is appropriate at this stage.

For patients with gastric ulcers, a follow-up endoscopy is indicated 8 to 12 weeks after treatment to confirm ulcer healing and to obtain biopsies ruling out underlying malignancy. This follow-up is not required for uncomplicated duodenal ulcers, because duodenal ulcers are almost never malignant.

For patients diagnosed with gastric MALT lymphoma, the first-line treatment is H. pylori eradication therapy alone for early-stage (stage I or II) disease. Repeat endoscopy with biopsy is performed to document lymphoma regression.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The single most common mistake students make with H. pylori gastritis questions is using serology to confirm eradication. IgG antibodies remain detectable long after the infection has been cleared, so a positive serology after treatment is meaningless. The correct test of cure is always the urea breath test or stool antigen test, performed at least 4 weeks after finishing antibiotics and 2 weeks after stopping PPIs.

A second frequent error involves forgetting to hold PPIs before non-invasive testing. A vignette may describe a patient already on a proton pump inhibitor who undergoes a urea breath test that comes back negative. The expected recognition is that this is a likely false negative caused by PPI suppression of bacterial urease activity, and the next step is to repeat the test after an appropriate washout period.

Students also confuse the clinical consequences of the two gastritis patterns. When a vignette describes a young patient with a duodenal ulcer, the underlying mechanism is antral-predominant gastritis with increased acid output. When a vignette describes an older patient with gastric atrophy, intestinal metaplasia, or a gastric mass, the mechanism is corpus-predominant gastritis with decreased acid and a precancerous pathway. Both are caused by the same organism, and the distinction is driven by anatomy, not by different bacterial strains.

Finally, do not overlook the MALT lymphoma connection. When a question describes a low-grade gastric B-cell lymphoma, the expected first step in management is H. pylori eradication, not chemotherapy or radiation. This is a classic "next best step" question designed to test whether the student understands that removing the antigenic stimulus can induce lymphoma regression.

The core competency being tested across all H. pylori questions is the ability to link the organism's pathophysiology to its clinical pattern, select the correct diagnostic test for the clinical scenario, sequence treatment and follow-up appropriately, and avoid the serology and PPI testing traps.