Severe nutritional complications after bariatric surgery in Ontario adults: a population-based descriptive study

BACKGROUND: Bariatric surgery is the most effective treatment for severe obesity but carries potential for significant complications. Severe postoperative nutritional complications are believed to be rare, but few studies have described them. OBJECTIVES: Describe incidence and factors associated with severe nutritional complications after adult bariatric surgery. SETTING: Multicenter publicly funded Ontario Bariatric Network. METHODS: Retrospective population-based descriptive study of Ontario adults undergoing bariatric surgery between January 1, 2009 and December 31, 2015. The primary outcome was a severe nutritional complication (hospital admission with malnutrition or nutrient deficiency). Major nutrient deficiencies, invasive nutrition support, and death are described. Data were obtained from administrative databases in ICES. Detailed patient data were also obtained for a subset of patients participating in the Ontario Bariatric Registry. RESULTS: Of Ontario adults, 18,783 (81.8% female, mean age 45.1 ± 10.6 yr) underwent bariatric surgery during the study period (88.8% Roux-en-Y gastric bypass, 10.8% sleeve gastrectomy). There were 57.1% in Ontario Bariatric Registry, with mean preoperative body mass index 49.3 ± 8.0 kg/m². Of patients, 381 (2%) experienced a severe nutritional complication. The incidence rate was 4.5 per 1000 person-years of follow-up and risk was constant over time. The most common deficiencies were iron and protein. Factors associated with severe nutritional complication included younger age, major co-morbidities, low socioeconomic status, surgical or perioperative complication, imperfect follow-up attendance, greater weight loss during the first year, and drop in albumin at 6 months. CONCLUSIONS: The risk of severe nutritional complications after bariatric surgery is low but similar to that of other major bariatric surgery complications.