Gastric Bypass Associated Hyperammonemia (GaBHA): A Case Study, Scoping Review of the Literature, and Proposed New...

Background/Objectives: GaBHA syndrome (gastric bypass hyperammonemia) is an emerging new syndrome primarily in women who had prior Roux-en-Y gastric bypass surgery (RYGB) and then developed non-cirrhotic hyperammonemia with a high case-fatality ratio. Genetic and nutritional deficiencies have been implicated in the pathogenesis of this clinical condition, but none has been proven. We present an illustrative case and do a scoping review of the current literature in 58 patients with this diagnosis. Methods: A retrospective scoping literature review was utilized to identify patients who fulfilled 1. RYGB surgery, and 2. Hyperammonemic encephalopathy following the PRISMA extended checklist. We searched PubMed, MedLine, SCOPUS, and Web of Science databases. Results: We described the classic presenting symptoms and laboratory findings of this syndrome. We confirmed the female predominance (93%) and the high case-fatality ratio (32%). We then presented a novel hypothesis contending that arginine deficiency ultimately leads to a functional deficiency of the ornithine transcarbamolyase (OTC) enzyme, leading to the non-cirrhotic life-threatening hyperammonemia. Our hypothesis may also explain the high incidence of hypoglycemia found in these patients as we found in our search. Our proposed hypothesis may also be relevant to the occurrence of hyperammonemia in some solid organ transplant recipients. Conclusions: GaBHA syndrome is emerging as an important potential adverse outcome after RYGB surgery. It has a female predominance and a high case-fatality ratio. Arginine deficiency may explain the emergence of a functional OTC deficiency, which then leads to the severe hyperammonemia, and may also explain the frequent occurrence of hypo-glycemia in these patients.