Upper Endoscopy for Vitamin B12 Deficiency

Diagnostic Approach

Vitamin B12 deficiency with negative antibodies may still indicate atrophic gastritis, which requires histological confirmation through endoscopy, as recommended by the American Gastroenterological Association 1
Corpus-predominant atrophic gastritis can cause vitamin B12 deficiency due to reduced intrinsic factor and gastric acid secretion, even in seronegative cases, with a reported prevalence in patients with vitamin B12 deficiency 2
Atrophic gastritis is a common cause of B12 deficiency and requires histopathologic confirmation through gastric biopsies, following the updated Sydney protocol for obtaining topographical biopsies 1
When performing EGD, biopsies should be placed in 2 separate specimen jars labeled antrum/incisura and body to properly assess the extent and severity of atrophic gastritis 3

Despite negative antibody tests, histological examination can reveal corpus-predominant atrophic gastritis with loss of parietal cells, explaining B12 malabsorption, with a strength of evidence supporting the importance of histological diagnosis 2
The diagnosis of atrophic gastritis requires histopathological confirmation regardless of serological findings, as stated by the American Gastroenterological Association 1
Evaluate for iron deficiency alongside B12 deficiency, as both can occur in atrophic gastritis, with a reported association between the two conditions 2

During endoscopy, test for H. pylori infection, as it can contribute to atrophic gastritis and B12 deficiency, with a recommended testing protocol 4
Consider surveillance endoscopy every 3 years for patients diagnosed with advanced atrophic gastritis due to increased risk of gastric cancer and neuroendocrine tumors, as recommended by the American Gastroenterological Association 5, 6

The American Gastroenterological Association recommends administering folic acid 1 mg daily concomitantly if folate deficiency is present in patients with vitamin B12 deficiency 7
Patients with confirmed advanced atrophic gastritis require surveillance endoscopy every 3 years due to increased risk of gastric cancer and neuroendocrine tumors, and should be monitored for iron deficiency and progression of atrophy 7

The American College of Gastroenterology recommends initiating oral vitamin B12 replacement at 1,000 mcg daily as first-line therapy, with recheck of vitamin B12 levels at 40 days to confirm adequate response, and reserving intramuscular B12 for non-responders to oral therapy 7