Defining Global Benchmarks in Bariatric Surgery

A Retrospective Multicenter Analysis of Minimally Invasive Roux-en-Y Gastric Bypass and Sleeve Gastrectomy

Daniel Gero, MD; Dimitri A. Raptis, MD, MSc, PhD; Wouter Vleeschouwers, MD; Sophie L. van Veldhuisen, MD; Andres San Martin, MD; Yao Xiao, MD; Manoela Galvao, MD; Marcoandrea Giorgi, MD; Marine Benois, MD; Felipe Espinoza, MD; Marianne Hollyman, MD, PhD; Aaron Lloyd, MPH; Hanna Hosa, MD; Henner Schmidt, MD; José Luis Garcia-Galocha, MD; Simon van de Vrande, MD; Sonja Chiappetta, MD; Emanuele Lo Menzo, MD; Cristina Mamédio Aboud, RN, MSc; Sandra Gagliardo Lüthy; Philippa Orchard, MD; Steffi Rothe, MBA; Gerhard Prager, MD; Dimitri J. Pournaras, MD, PhD; Ricardo Cohen, MD; Raul Rosenthal, MD; Rudolf Weiner, MD; Jacques Himpens, MD, PhD; Antonio Torres, MD, PhD; Kelvin Higa, MD; Richard Welbourn, MD; Marcos Berry, MD; Camilo Boza, MD; Antonio Iannelli, MD; Sivamainthan Vithiananthan, MD; Almino Ramos, MD; Torsten Olbers, MD, PhD; Matias Sepúlveda, MD; Eric J. Hazebroek, MD, PhD; Bruno Dillemans, MD; Roxane D. Staiger, MD; Milo A. Puhan, MD, PhD; Ralph Peterli, MD; Marco Bueter, MD, PhD


Annals of Surgery. 2019;270(5):859-867. 

In This Article


Study Design

The establishment of benchmarks in BS followed a standardized methodology, previously applied in visceral surgery.[2,6–8,15] We performed a multicentric retrospective cohort study based on prospective institutional databases to define best achievable surgical outcomes in primary laparoscopic RYGB and SG.

First, a large patient cohort from international expert centers was gathered via personal invitation of distinguished surgeons. Eligible centers had to meet the criteria listed in Table 1.[16–33] The final collaborative consortium included 19 centers: 12 from Europe (Arnhem, Basel, Brussels/Dendermonde, Bristol, Bruges, Gothenburg, Madrid, Nice, Offenbach, Taunton, Wien, and Zurich), 3 from USA (Fresno, Providence, Weston), and 4 from South America (Santiago de Chile, São Paulo [2 centers in each city]).

Second, to define the "benchmark bariatric patient," evidence-based criteria associated with a lower postoperative complication rate were applied (Table 1). Each center had to include all consecutive benchmark cases with a documented follow-up of minimum 90-days (including mortality), operated over a 5-year period (June 1, 2012 to May 31, 2017).

Third, relevant outcome indicators for surgical quality were assessed. To adjust for variability, median values of continuous variables and the proportions of categorical variables were calculated for each participating center. Benchmark cutoffs, indicating "best achievable" result for each outcome indicator, were set at the 75th percentile of the centers' median values. Additionally, range and median (ie, "premium result") of each indicator was computed. The study protocol was preregistered on (NCT03440138). The approval of the Cantonal Ethics Committee of Zurich, as well as of the ethical board of each respective center, was obtained before data analysis.

Outcome Variables of Interest

Local investigators retrieved patient-specific data and uploaded them to a secure and anonymized online data-entry management system provided by the University Hospital Zurich.[34] Data were audited and checked for completeness by DG and included baseline characteristics of patients (age, sex, body-mass index [BMI], comorbidities), operation characteristics, inpatient complications by severity according to the Clavien–Dindo (CD) grading system,[35,36] length of stay, readmissions (time from operation, reason, and treatment), last follow-up, and yearly postoperative BMI. To enable the assessment of cumulative morbidity over time, the Comprehensive Complication Index (CCI) was used.[37] The CCI expresses morbidity on a continuous numeric scale from 0 (no complications) to 100 (death) by weighing all postoperative complications according to the CD classification. Relevant bariatric complications, such as staple line/anastomotic leak, anastomotic or gastric tube stenosis, internal hernia, marginal ulcer at the gastrojejunostomy, were additionally analyzed.[16,38,39] Postoperative weight loss was expressed as %total weight loss, and excess body mass index loss (EBMIL) (% excess BMI loss, with BMI = 25 kg/m2 considered as normal).[40] Benchmark cutoffs for overall inpatient costs were calculated separately for patients with or without any surgical complications by using the algorithm developed by Staiger et al.[41]

Proof of Concept

To validate the need for outcome benchmarks in BS, we applied 3 complementary measures. First, we collected data on 90-day mortality of all RYGB and SG cases operated during the study period. Second, we selected 1 participating center (Number 2 in Figure 1) to provide outcome data of all nonbenchmark RYGB cases. Third, we identified previously published studies by the participating centers reporting 30-day major complications rates in consecutive and secondary RYGB cohorts to objectify the additional burden of "high-risk" cases on the early postoperative morbidity.

Figure 1.

Case mix of elective bariatric surgery (BS) in participating centers over the 5-yr inclusion period (June 2012–May 2017). Percentages show the proportion of benchmark Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) cases within the total elective BS caseload.

Statistical Analysis

Centers that contributed with <30 cases per type of BS (RYGB or SG) were excluded from analyses in the respective operation subgroup.[42] Discrete variables were described using count (percent), and continuous variables were described using medians (with interquartile range). Kaplan–Meier curve was used to describe the occurrence of postoperative CD >II complications over observation time. Statistical analysis was performed using the R software 3.5.1 (R Foundation, Vienna, Austria).