Volume‒outcome relationships in bariatric surgery: a rapid review

The treatment of obesity is complex and requires long-term multidisciplinary care. While behavioral, pharmacological and psychological therapies are integral, bariatric surgery remains the most effective intervention. Therapeutic success is influenced by factors such as comorbidities and potentially by the experience of the treatment facilities. This rapid review evaluates the evidence of volume-outcome associations in bariatric surgery, focusing on the endpoint of mortality.

We performed a rapid review of the literature published after 2000, including adult patients (≥18 years) who underwent bariatric surgery for weight loss, or weight loss and diabetes management. Searches across EMBASE, MEDLINE, PubMed, and Cochrane Trials yielded 3540 records. The primary outcome was mortality; secondary outcomes included complications, morbidity and hospital stay. Mortality results were stratified by type of mortality and synthesized according to volume type (hospital or surgeon). Study quality was assessed using the ISPOR and ROBINS-E tools. An additional synthesis was conducted for studies above a quality score cutoff.

Thirty-six studies met the inclusion criteria. Of these, 12 studies examined the association between hospital volume and mortality, and five studies focused on surgeon volume. Eight of the hospital volume studies and four of the surgeon volume studies reported a positive association with reduced mortality; some showed mixed results. Most studies also linked higher volumes to fewer complications and shorter hospital stays. However, the focus was predominantly on hospital volume and short-term mortality, with limited evaluations of long-term outcomes or weight loss success. Overall study quality varied, with noted limitations including arbitrary volume thresholds.

Higher hospital and surgeon volumes were associated with lower short-term mortality, fewer complications and shorter hospital stays. The association was more pronounced in higher-quality studies. Future research should aim to standardize volume definitions to improve comparability and support policy efforts to centralize care and enhance patient outcomes.