Introduction: Roux-en-Y gastric bypass (RYGB) can precipitate protein-caloric malnutrition and micronutrient deficiencies. Sonographically guided endoscopic reversal (ER) via deployment of a stent from the gastric pouch to the remnant stomach is emerging as a novel option for increasing intestinal transit time and increasing absorptive surface area. In this investigation, short-term nutritional outcomes after endoscopic reversal for malnutrition were assessed. Methods: Patients (age ≥ 18) who underwent ER of RYGB for malnutrition from a single academic health center in Minneapolis over a 7-year period (2015-2021) were reviewed. Nutrition status (assessed by a registered dietitian (RD) or a gastroenterologist (GI)), mode of nutrition (per oral (PO), tube feed (TF), or total parenteral nutrition (TPN)), weight and body-mass index (BMI) were obtained pre-procedurally, at 6 months, and at one year post-procedurally. Results: Seventeen patients underwent ER for severe protein caloric malnutrition or dependence on TF / TPN. In this cohort, at the time of the ER procedure, median age was 49 [IQR 46, 58] years and median BMI was 25.2 [IQR 21.18, 29.03] kg/m2, 70% of patients were female, and 82% were White, and 96% had health insurance. Weight and BMI were not significantly different at 6-month or at one year follow-up (P >0.05; Figure demonstrates individual weight trends). At 6 months post-ER, 2 patients were no longer malnourished by RD/GI assessment and only on PO nutrition; 3 patients previously on TPN were liberated from TPN. A panel of laboratory values including markers of protein calorie malnutrition (e.g. albumin), renal function (e.g. creatinine and GFR) and micronutrients (e.g. Vitamin B12) were not significantly different at 6-month or at one year follow-up (P >0.05; Table). In all patients, access to the remnant was maintained throughout the study period and no complications were noted after the procedure. Conclusion: ER is a nuanced, advanced technique useful for when remnant access is desired in RYGB patients, and is safe in experienced hands. Despite small sample size, this investigation revealed that ER of RYGB may prevent worsening weight loss, and worsening macro and micro-nutrient deficiencies; though improvement in weight and nutritional parameters was not observed. As ER affords patients a potential alternative to revisional bariatric surgery, further studies are warranted to examine longer-term nutritional and medical outcomes.Figure 1.: Individual weight trends before RYGB Endoscopic Reversal and at 6 months and 1 year following RYGB Endoscopic Reversal Table 1. - Pre-procedure Post-procedure at 6 months Post-procedure at 1 year Malnutrition Status by dietitian or gastroenterologist assessment (n, %) N=17 N=17 N=9 Severe Malnutrition or on TF / TPN 17 (100%) 15 (88%) 8 (89%) Moderate 0 0 0 Non-severe 0 0 0 Not malnourished 0 2 (12%) 1 (11%) Nutrition Route N=17 N=17 N=9 Oral intake (PO) 6 6 2 Tube feeding (TF) 3 6 3 Total parenteral nutrition (TPN) 8 5 4 Weight / Body Mass Index, median (IQR) N=17 N=15 N=9 Weight (Kg) 64.8 (54.3, 78.1) 68.4 (57.9, 83.6) 67.8 (63.0, 71.1) BMI (Kg/m2) 25.2 (21.2, 29.0) 25.1 (23.1, 30.3) 23.2 (20.5, 24.9) Nutritional Laboratory Values, median (IQR) N * N * ** Albumin (g/dL) 2.6 (2.3, 3.1) 2.4 (1.92, 3.05) x Prealbumin (mg/dL) 14 (10, 15) 14 (8, 16) x Hemoglobin (g/dL) 9.4 (8.8, 11.5) 10.6 (8.8, 12.4) x Creatinine (mg/dL) 0.88 (0.62, 0.99) 0.72 (0.66, 1.06) x Glomerular filtration rate (mL/min) 86 (61, 90) 84 (52, 90) x Iron (ug/dL) 59 (29, 71) 34.5 (19, 49.3) x Ferritin (ng/mL) 113 (27.8, 409) 39 (28.5, 114) x Vitamin B12 (pg/mL) 893 (554, 1405) 1271 (731, 1422) x Folate (ng/mL) 6.6 (5.4, 21.4) 10.6 (6.5, 11.8) x Vitamin D (ug/L) 14 (13, 39) 24.5 (14.5, 27.8) x Zinc (ug/dL) 56 (55, 71) 56.5 (48, 62) x *Various different sample size based on lab availabilities.**1 Year nutritional laboratory values not assessed.