The relationship between hospital volume and outcome in bariatric surgery at academic medical centers

Abstract

Objective: To examine the effect of hospital volume of bariatric surgery on morbidity, mortality, and costs at academic centers.

Summary background data: The American Society for Bariatric Surgery recently proposed categorization of certain bariatric surgery centers as "Centers of Excellence." Some of the proposed inclusion criteria were hospital volume and operative outcomes. The volume-outcome relationship has been well established in several complex abdominal operations; however, few studies have examined this relationship in patients undergoing bariatric surgery.

Methods: Using the International Classification of Diseases, 9th edition, diagnosis and procedure codes, we obtained data from the University HealthSystem Consortium Clinical Data Base for all patients who underwent Roux-en-Y gastric bypass for the treatment of morbid obesity between 1999 and 2002 (n = 24,166). Outcomes of bariatric surgery, including length of hospital stay, 30-day readmission, morbidity, observed and expected (risk-adjusted) mortality, and costs were compared between high-volume (>100 cases/year), medium-volume (50-100 cases/year), and low-volume hospitals (<50 cases/year).

Results: There were 22 high-volume (n = 13,810), 27 medium-volume (n = 7634), and 44 low-volume (n = 2722) hospitals included in our study. Compared with low-volume hospitals, patients who underwent gastric bypass at high-volume hospitals had a shorter length of hospital stay (3.8 versus 5.1 days, P < 0.01), lower overall complications (10.2% versus 14.5%, P < 0.01), lower complications of medical care (7.8% versus 10.8%, P < 0.01), and lower costs ($10,292 versus $13,908, P < 0.01). The expected mortality rate was similar between high- and low-volume hospitals (0.6% versus 0.6%), demonstrating similarities in characteristics and severity of illness between groups. The observed mortality, however, was significantly lower at high-volume hospitals (0.3% versus 1.2%, P < 0.01). In a subset of patients older than 55 years, the observed mortality was 0.9% at high-volume centers compared with 3.1% at low-volume centers (P < 0.01).

Conclusions: Bariatric surgery performed at hospitals with more than 100 cases annually is associated with a shorter length of stay, lower morbidity and mortality, and decreased costs. This volume-outcome relationship is even more pronounced for a subset of patients older than 55 years, for whom in-hospital mortality was 3-fold higher at low-volume compared with high-volume hospitals. High-volume hospitals also have a lower rate of overall postoperative and medical care complications, which may be related in part to formalization of the structures and processes of care.

FIGURE 1. Volume of Roux-en-Y gastric bypass according to year, 1999–2002.

FIGURE 2. Observed-to-expected in-hospital mortality ratio for a subset of patients ≥ 55 years according to volume of bariatric surgery. *P < 0.05 compared with high-volume hospitals.