What is the anatomy, function, common pathologies, diagnostic workup, and treatment of the gastric antrum?

Gastric Antrum: Anatomy, Function, Pathology, Diagnosis, and Treatment

Anatomical Definition and Location

The gastric antrum is the distal portion of the stomach located between the corpus and the pyloric sphincter, serving as the terminal grinding chamber before gastric contents enter the duodenum. 1 The antrum begins at the incisura angularis on the lesser curvature and extends distally to the pylorus, typically measuring 2-3 cm proximal to the pyloric sphincter. 2 Unlike the corpus which contains oxyntic (parietal) cells, the antrum contains pyloric glands that secrete gastrin and mucus. 2

Physiological Function

Motor Function

• The antrum generates powerful peristaltic contractions that grind solid food particles and propel gastric contents toward the pylorus. 3 These contractions develop high pressures when the antrum is separated from the body by peristaltic waves, functioning as a mechanical pump. 3
• The antrum works in coordination with the pylorus to perform "gastric sieving," selectively retaining particles too large for intestinal delivery while allowing isotonic fluids to pass. 4

Endocrine Function

• Gastrin-producing G cells in the antral mucosa regulate gastric acid secretion through hormonal feedback mechanisms. 5 Normal antral function includes inhibitory reflex pathways that suppress both gastrin release and parietal cell acid secretion when appropriate. 5

Common Pathologies

H. pylori-Associated Antral Gastritis

Antral-predominant H. pylori gastritis is the most common pathology affecting this region and strongly correlates with duodenal ulcer disease. 6 The mechanism involves selective blockade of normal inhibitory reflex pathways from the antrum to gastrin cells and parietal cells, resulting in hypergastrinemia and increased acid secretion. 5 This creates the "duodenal ulcer phenotype" of gastritis. 6

Atrophic Gastritis Patterns

• H. pylori-associated atrophic gastritis (HpAG) characteristically initiates in the antrum and progresses proximally toward the corpus over time. 2, 7 The atrophic border can be classified using the Kimura-Takemoto system, with severe/extensive atrophy (O2-O3 types) carrying significantly higher gastric cancer risk than mild atrophy (C1-C2 types). 2
• Autoimmune gastritis (AIG) demonstrates the opposite pattern with corpus-predominant atrophy and characteristic antral sparing. 2, 7 This distinction is critical for diagnosis and prognosis. 7

Intestinal Metaplasia

• The presence of intestinal metaplasia in the antrum almost invariably indicates underlying atrophic gastritis and signals increased gastric cancer risk. 2, 7 Incomplete (colonic-type) intestinal metaplasia carries 3-fold higher cancer risk than complete type. 8

Type 1 Gastric Neuroendocrine Tumors

Type 1 gastric NETs are associated with antrum-sparing type A chronic atrophic gastritis and hypergastrinemia. 2 These tumors are typically multiple, small (≤2 cm), and have favorable prognosis compared to type 3 sporadic NETs. 2

Diagnostic Workup

Endoscopic Evaluation

High-definition white-light endoscopy (HD-WLE) with narrow-band imaging (NBI) should be performed with systematic examination and photographic documentation of the antrum along both lesser and greater curvatures. 2, 9 Key endoscopic features include:

• Atrophic mucosa appears pale with increased visibility of submucosal vessels due to mucosal thinning and loss of rugal folds. 2
• Intestinal metaplasia demonstrates the "light blue crest" sign (fine blue-white lines on epithelial crests) with 90% sensitivity and specificity, and "white opaque substance" with 100% specificity. 2

Biopsy Protocol

The updated Sydney protocol mandates 5 separate biopsies in individually labeled jars: 2 from the antrum (lesser and greater curvature within 2-3 cm of pylorus), 2 from the corpus, and 1 from the incisura angularis. 2, 9 This protocol achieves close to 100% sensitivity for H. pylori detection and proper risk stratification. 2

Critical pitfall: Do not skip the incisura angularis biopsy, as atrophy and intestinal metaplasia frequently involve this site. 2, 8 If cost is prohibitive, minimally use 2 jars labeled "antrum/incisura" and "body." 2

H. pylori Testing

All patients with antral pathology should undergo H. pylori testing using the biopsy specimens, urea breath test, or monoclonal stool antigen test. 2, 8 The Sydney biopsy protocol has nearly 100% sensitivity for identifying H. pylori colonization. 2

Serologic Testing

• For suspected autoimmune gastritis with antral sparing, check parietal cell antibodies (PCA) and intrinsic factor antibodies (IFA). 2 PCA is most sensitive but can be falsely positive in H. pylori infection; IFA is more specific. 2
• Serum pepsinogen testing (PG I <70 μg/L and PG I:II ratio <3.0) indicates severe corpus atrophy but is not routinely available in the United States. 2

Functional Testing

Antroduodenal manometry can assess antral contractility and coordination with duodenal motor function. 2 Decreased antral contractility and reduced postprandial distal antral motility index correlate with impaired gastric emptying. 2 However, this is primarily used when gastroparesis is suspected rather than for routine antral pathology evaluation. 2

Treatment Approach

H. pylori Eradication (First-Line for Most Antral Pathology)

Bismuth quadruple therapy for 14 days is the preferred treatment: bismuth subcitrate 120 mg four times daily plus two antibiotics (amoxicillin, tetracycline, or metronidazole) plus high-potency PPI. 9, 8 This addresses the underlying cause in the vast majority of antral gastritis cases. 8

Confirm eradication 4-6 weeks after completing therapy using non-invasive testing (urea breath test or stool antigen)—do not rely on symptom resolution alone. 9, 8 This is a critical pitfall to avoid. 9

Acid Suppression

High-potency PPIs are first-line for symptom relief and mucosal healing: esomeprazole 20-40 mg twice daily, rabeprazole 20 mg twice daily, or lansoprazole 30 mg twice daily. 8 Continue PPI therapy during and after H. pylori eradication for 4-8 weeks total. 8

Management Based on Histologic Findings

For Atrophic Gastritis with Intestinal Metaplasia

All patients with intestinal metaplasia require H. pylori eradication (strong recommendation, moderate quality evidence). 8 After eradication:

• Patients with extensive atrophy and/or multifocal/incomplete intestinal metaplasia should undergo endoscopic surveillance every 3 years, with shorter intervals for multiple risk factors. 9
• Screen for and treat iron and vitamin B12 deficiencies, particularly with extensive atrophic changes. 8

For Dysplasia

• Low-grade or indefinite dysplasia requires confirmation by an experienced GI pathologist, H. pylori eradication if present, then repeat endoscopy with biopsies. 9
• High-grade dysplasia or early gastric cancer requires immediate referral for endoscopic submucosal dissection at an expert center. 9

For Type 1 Gastric NETs

Management is size-based: observe or resect lesions <1 cm, endoscopic resection for 1-2 cm lesions, and surgical referral with cross-sectional imaging for lesions >2 cm due to metastatic risk. 9

Gastroparesis with Antral Dysfunction

If antroduodenal manometry demonstrates decreased antral contractility:

• Dietary modification: frequent small meals, liquid-based foods (soups), low fat and fiber content. 2
• Prokinetic agents: metoclopramide or erythromycin (oral or IV). 2 Domperidone is available outside the United States. 2
• Antiemetics as needed: prochlorperazine, trimethobenzamide, promethazine, or 5-HT3 antagonists. 2

Critical Pitfalls to Avoid

• Never use inadequate antibiotic duration (<14 days) or insufficient PPI dosing during H. pylori eradication. 8
• Never assume H. pylori eradication eliminates cancer risk—established atrophic changes require ongoing surveillance regardless of eradication success. 9
• Never fail to obtain separate antral and corpus biopsies in labeled jars, as this prevents accurate risk stratification. 9, 8
• Never rely solely on symptom resolution to confirm H. pylori eradication—objective testing is mandatory. 9