COBALAMIN DEFICIENCY and SMALL BOWEL BACTERIAL OVERGROWTH: A COMMON ASSOCIATION

Abstract

Background Bacterial overgrowth may cause cobalamin deficiency through competition for dietary cobalamin in the small intestine. The objective of this study was to prospectively determine the prevalence of small bowel bacterial overgrowth in patients with documented cobalamin deficiency in a tertiary referral centre.Methods Patients identified with cobalamin deficiency underwent diagnostic investigations including: Endoscopy (with gastric antrum, gastric body and duodenal biopsies and duodenal aspirate), 14C‐D‐Xylose breath test, intrinsic factor antibody, anti‐endomysial antibody and red cell folate level. ‘Definite’ small bowel bacterial overgrowth was defined as either a positive 14C‐D‐Xylose breath test or > 100 000 CFU/mL of culture of duodenal aspirate. ‘Suspected’ small bowel bacterial overgrowth was defined as an elevated red cell folate in the absence of supplemental folate therapy.Results Over a 2‐year period, 62 patients with cobalamin deficiency were identified, of whom, 26 (42%) had ‘definite’ small bowel bacterial overgrowth, whilst a further nine (15%) had ‘suspected’ small bowel bacterial overgrowth. Nineteen (31%) had pernicious anaemia, and no cause for cobalamin deficiency could be found in eight (13%) patients. The diagnosis found in the remaining patients included coeliac disease (4), Crohn's Disease (1), gastric resection (2), vegan (2), homozygotes of the MTHFR gene (C677T) mutation (2), and one had enteropathy associated with common variable immunodeficiency (CVID). ‘Definite’ small bowel bacterial overgrowth was found to coexist with nine of the 19 cases of pernicious anaemia, two coeliac subjects, one CVID enteropathy and one patient with the MTHFR gene mutation.Conclusion Small bowel bacterial overgrowth is commonly associated with cobalamin deficiency.