The obesity paradox: Underweight patients are at the greatest risk of mortality after cholecystectomy.

BACKGROUND

Elevated body mass index is a risk factor for gallstone disease and cholecystectomy, but outcomes for low body mass index patients remain uncharacterized. We examined the association of body mass index with morbidity, mortality, and resource use after cholecystectomy.

METHODS

The 2005 to 2016 American College of Surgeons National Surgical Quality Improvement Program was retrospectively analyzed for adult patients undergoing laparoscopic and open cholecystectomy. Patients were stratified into 5 groups: body mass index <18.5 (underweight), body mass index 18.5 to 24.9 (normal weight), body mass index 25 to 29.9 (overweight), body mass index 30 to 34.9 (class I obesity), body mass index 35 to 39.9 (class II obesity), and body mass index ≥40 (class III obesity). Multivariable regressions identified independent associations of covariates with 30-day mortality, complications, and resource use.

RESULTS

Of 327,473 cholecystectomy patients, 1.0% were underweight, 19.5% normal weight, 30.3% overweight, 24.0% class I obesity, 13.5% class II obesity, and 11.7% class III obesity. After multivariable analysis, underweight patients had a higher risk of mortality (adjusted odds ratio = 1.53; P = .029) and postoperative bleeding (adjusted odds ratio = 1.45; P = .011) relative to normal weight patients. Conversely, class III obesity patients had lower mortality (adjusted odds ratio = 0.66; P = .005) but increased operative time (β = 10.2 minutes; P < .001), wound infection (adjusted odds ratio = 1.38; P < .001), and wound dehiscence (adjusted odds ratio = 2.20; P < .001). Hospital duration of stay and readmission rates were highest for underweight patients.

CONCLUSION

Underweight patients experience increased risk of mortality and readmission, while class III obesity patients have higher rates of wound infection and dehiscence as well as prolonged operative time. These findings may guide choice of intervention.