Roux-en-Y gastric bypass (RYGB) surgery is one of the most commonly performed bariatric procedures for weight loss in humans. However, this procedure is not risk-free, and patients may experience complications that include small bowel obstruction, gastrointestinal bleeding, chronic diarrhea, ulcers, malnutrition, and anemia. In particular, anemia is a recognized long-term complication and can be severe. Rats have been used as a model to study the effects of gastric bypass surgeries. They can experience similar complications as people, but the development of severe anemia has not previously been reported in rats. We observed 2 cases of severe anemia in female Sprague-Dawley rats after RYGB surgery. These cases prompted us to further investigate the frequency and severity of anemia after RYGB in rats. Blood work and necropsies were performed on 9 additional female Sprague-Dawley rats (5 with RYGB, 4 with sham surgery). In these 9 rats, only one had signs of clinical anemia. These 3 anemic rats displayed moderate to severe pallor of the eyes and ears. Necropsy findings in anemic RYGB rats included pale internal organs and eccentric heart enlargement, which led to a significantly higher heart:body weight ratio in RYGB rats as compared with sham controls. Anemic rats had either a macrocytic normochromic anemia, consistent with vitamin B12 or folate deficiency, or microcytic hypochromic anemia, indicative of iron deficiency. Researchers who perform RYGB surgery in rats should be aware of the potential complication of severe anemia. Plans for the diagnosis and management of this complication and the development of criteria for humane endpoints for severe anemia are recommended as a refinement to these studies.
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