Severe anemia after Roux-en-Y gastric bypass: a cause for concern

Background: The current popularity of metabolic surgery has led to increasing attention to longterm nutritional complications. Objective: The purpose of this retrospective study is to accurately define the long-term incidence of clinically significant anemia after Roux-en-Y gastric bypass (RYGB) and to identify factors that contribute to increased risk. Methods: The study cohort consisted of 2116 patients who underwent RYGB with necessary laboratory information available, and with longitudinal follow-up available (mean 5.3 +/- 3.3 yr). A concurrent cohort of nonoperated patients matched for age, sex, body mass index, and baseline hemoglobin was identified (N = 1126). The RYGB and control cohorts were followed longitudinally to estimate the percent that develop mild, moderate, or severe anemia using Kaplan-Meier analysis. Predictors of severe anemia within the RYGB cohort were identified using Cox regression. Results: The percent developing postRYGB mild, moderate, and severe anemia was 27%, 9%, and 2% at 1 year postRYGB and increased to 68%, 33%, and 11% at 5 years postRYGB. As compared with the nonoperated control cohort, the RYGB cohort was more likely to develop mild anemia (hazard ratio [HR] = 1.36, P <. 001), moderate anemia (HR = 1.75, P < .001), and severe anemia (HR = 1.87, P < .001). Severity of anemia was associated with an increasing percentage of microcytosis (P < .0001). Clinical factors independently associated with an increased risk of severe anemia within the RYGB cohort included females and males >40 years of age (HR = 2.97, 95% confidence interval [CI] = 1.14, 7.75, P = .026), preoperative anemia (HR = 1.65, 95% CI = 1.19, 2.29, P = .0029), preoperative low ferritin level (HR = 2.28, 95% CI = 1.39, 3.74, P = .0029), and a rapid 6-month weight loss trajectory (HR = 1.71, 95% CI = 1.22, 2.38, P = .0018). Conclusions: The long-term incidence of clinically significant anemia after RYGB is alarmingly high and warrants more detailed study. (C) 2018 American Society for Metabolic and Bariatric Surgery. All rights reserved.