Same-Day Discharge after Metabolic Bariatric Surgery: Methodological Heterogeneity, Discharge Success Rates and 30-Day Safety Outcomes - A Systematic Review.

BACKGROUND: Same-day discharge after metabolic bariatric surgery (MBS) is increasingly practiced, but the validity of pooling published evidence remains unknown. Methodological heterogeneity in patient selection and discharge criteria may prevent valid meta-analysis. We systematically reviewed same-day discharge studies to assess whether criteria definitions are sufficiently standardized to permit evidence synthesis. METHODS: We searched CENTRAL, PubMed, and EMBASE (inception to January 15, 2025) for studies reporting same-day discharge after MBS. We extracted inclusion criteria, exclusion criteria, and discharge criteria verbatim from each study and performed thematic content analysis to identify common components. Primary outcome was the proportion of studies using unique (non-shared) criteria definitions. Secondary outcomes included same-day discharge success rates and 30-day safety outcomes. RESULTS: 41 studies with 1,953,247 patients were included (4 RCTs, 23 cohorts, 11 registries, 3 other designs). Primary finding: Among 40 studies reporting inclusion criteria, 38 (95%) used unique definitions. Among 36 studies reporting exclusion criteria, 34 (94%) used unique definitions. Among 27 studies reporting discharge criteria, 27 (100%) used unique definitions. This heterogeneity was present across all study designs, including RCTs (100% unique criteria). Common components existed (age, BMI, ASA score) but thresholds varied dramatically. For example, age restrictions ranged from 16-69 years to 18-75 years across multiple different combinations. Secondary findings: Same-day discharge success rates ranged from 63 to 100% among studies reporting this outcome, but this variation primarily reflects discharge criteria stringency rather than true differences in feasibility or safety. Safety outcomes showed readmission rates of 0-20.8%, mortality of 0% in RCTs and cohort studies up to 0.12% in registries, and leak rates of 0-5.6%, but heterogeneous definitions prevented pooling. Stratified analysis revealed a differential safety signal, driven primarily by RYGB data, between sleeve gastrectomy and procedures involving an anastomosis. CONCLUSION: For the first time, this systematic review quantifies severe methodological heterogeneity in same-day discharge research (95-100% unique criteria definitions), violating fundamental assumptions for meta-analysis. Individual studies are well-conducted, but pooled estimates remain invalid when studies measure different interventions in different populations. Importantly, stratified analysis revealed a hypothesis-generating safety signal: same-day discharge after RYGB may carry higher mortality risk than after sleeve gastrectomy, reinforcing the need for procedure-specific standardization. International consensus on standardized patient selection criteria, discharge criteria definitions, and outcome reporting-separately for sleeve gastrectomy and anastomotic procedures-is urgently needed before additional studies are conducted.