BACKGROUND/AIMS: Metabolic bariatric surgery remains the most potent weapon we have against severe obesity and its metabolic consequences. Yet, its effects on the liver are far from uniform. Although restrictive and mixed procedures like sleeve gastrectomy and Roux-en-Y gastric bypass consistently improve metabolic dysfunction-associated steatotic liver disease (MASLD), hypoabsorptive operations carry a distinct and troubling risk of progressive liver injury. The available evidence, drawn predominantly from case series, registry data and retrospective analyses, suggests that this risk is not an all-or-nothing phenomenon but instead follows a conceptual gradient, one that correlates with the degree of intestinal malabsorption and, more specifically, with the extent of bile acid malabsorption. This review traces the evidence for this dose-dependent relationship from the historical disaster of the jejunoileal bypass to contemporary procedures like the biliopancreatic diversion and the single-anastomosis duodenal-ileal bypass. MATERIALS & METHODS: We explore the pathophysiological triad that drives this process-protein-energy malnutrition, bacterial overgrowth, and bile acid hepatotoxicity-supported by recent experimental evidence directly linking biliary limb length to liver injury. RESULTS: The review then contextualizes the discussion within associated multisystemic consequences, including de novo inflammatory bowel disease, severe metabolic bone disease, and a distinct discussion of the accelerated alcohol-associated liver disease that follows bariatric surgery. DISCUSSION: A synthesis of the available evidence supports the abandonment of a one-size-fits-all approach in favour of meticulous patient selection, precise and individualized surgical technique based on measured bowel length and a commitment to lifelong, intensive, multidisciplinary postoperative surveillance. CONCLUSION: Hypoabsorptive bariatric procedures carry a dose-dependent risk of progressive liver injury mediated by malabsorption, bacterial overgrowth and bile acid hepatotoxicity, necessitating individualized surgical planning and lifelong follow-up.
Papadia et al. (Mon,) studied this question.