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

The current popularity of metabolic surgery has led to increasing attention to long-term nutritional complications.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.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.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 males40 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).The long-term incidence of clinically significant anemia after RYGB is alarmingly high and warrants more detailed study.