One Anastomosis Gastric Bypass Versus Single Anastomosis Sleeve Jejunal Bypass: Does Duodenal Exclusion Matter?

BACKGROUND

One Anastomosis Gastric Bypass (OAGB) and Single Anastomosis Sleeve Jejunal Bypass (SASJ) represent two distinct single-anastomosis bariatric procedures that share similar anatomical configurations but differ fundamentally in their approach to duodenal transit. While OAGB excludes the duodenum completely from nutrient flow, SASJ partially reserves duodenal transit through a bipartition mechanism. This fundamental difference raises a critical question in metabolic surgery: how much does duodenal exclusion matter for weight loss and metabolic outcomes?

METHODS

We conducted a narrative review of the current literature comparing the anatomical, physiological, and clinical aspects of OAGB and SASJ, with particular emphasis on the role of duodenal exclusion in weight loss mechanisms, metabolic improvements, and nutritional consequences.

RESULTS

Both procedures demonstrate excellent weight loss (EW) outcomes with comparable excess weight loss (EWL) ranging from 70-85% at one year. Type 2 diabetes remission rates are high in both groups (80-98%). However, duodenal-excluding procedures may carry higher risks of micronutrient deficiencies, particularly iron, calcium, and vitamin B12. The foregut, hindgut, and holoileum hypotheses provide theoretical frameworks for understanding metabolic improvements. The holoileum hypothesis, proposed by Santoro, emphasizes the role of the elongated common channel containing pancreatic and biliary secretions in optimizing ileal endocrine function while minimizing malabsorption. Recent evidence suggests that hindgut stimulation through this mechanism may be the predominant factor regardless of duodenal exclusion.

CONCLUSIONS

Current evidence suggests that excellent metabolic outcomes can be achieved with complete or partial duodenal exclusion, provided adequate ileal stimulation is ensured through an elongated common channel (holoileum mechanism). SASJ may offer advantages in terms of nutritional preservation while maintaining metabolic efficacy. Prospective randomized trials directly comparing these procedures are warranted.