Gastric bypass versus sleeve gastrectomy: changes in postoperative cobalamin absorption — a systematic review

Abstract

Introduction: Obesity is a chronic inflammatory condition for which surgical treatment is the most effective method for sustained weight loss. In Brazil, Gastric Bypass and Sleeve Gastrectomy are the predominant techniques. However, the gastrointestinal modifications resulting from these procedures can lead to malabsorptive syndromes, notably cobalamin (vitamin B12) deficiency. Therefore, this study sought to compare and correlate changes in cobalamin absorption in the postoperative period of Gastric Bypass and Sleeve Gastrectomy techniques.Methodology: A systematic literature review was conducted in the Scopus, Lilacs, Medline, and PubMed databases in March 2023. Selection was independently performed by two reviewers, following PRISMA guidelines. Studies analyzing pre- and postoperative cobalamin levels in the techniques of interest were included. Articles with generic nutritional analyses or those focusing on other surgical techniques were excluded.Results: From 239 initial results, 18 articles were selected for full-text reading. After rigorous application of eligibility criteria, the final sample consisted of 8 articles. Evidence indicates that both restrictive and mixed techniques impact vitamin B12 metabolism, although the time for deficiency to manifest varies according to individual hepatic stores.Discussion/Conclusion: It was observed that cobalamin deficiency occurs in both restrictive and mixed procedures as a factual occurrence. The limited sensitivity of laboratory tests hinders early diagnosis. Due to hepatic reserves, reduced serum levels tend to manifest 2 to 5 years after surgery. Therefore, accurate diagnoses require longitudinal analyses, reinforcing the indispensability of long-term postoperative follow-up to prevent systemic damage.