The obesity paradox is a controversial hypothesis that obesity appears to be associated with lower mortality in certain diseases and procedures. A significant proportion of patients undergoing ERCP are obese, but whether the obesity paradox is reproducible in this patient population remains to be studied. In this study, we aim to investigate the relationship between obesity and the mortality of patients undergoing ERCP. The 2014 National Inpatient Sample database was analyzed by using ICD-9 codes for hospitalizations with a procedure code as therapeutic or diagnostic ERCP. Excluded hospitalizations included patients with age<20 or underweight, and elective admissions. The selected patients were categorized into normal weight (BMI: 19.0∼24.9), overweight (BMI: 25.0∼29.9), and obesity, which was further classified as grade 1 (BMI: 30.0∼34.9), grade 2 (BMI: 35.0∼39.9) and grade 3 (BMI: >=40.0 or morbid obesity). The primary outcome of interest was all-cause mortality and the secondary outcomes were the length of stay and total cost of the hospitalization. The odds ratios (ORs) of in-hospital outcomes of obese/overweight patients were calculated relative to those with normal weight. Multivariate regression was used to adjust for age, gender, race, incomes, insurance, hospital characteristics, comorbidities, types and indications of ERCP. We repeated the above analysis in a restricted cohort by excluding patients who were smokers, alcoholics, or had any comorbidities defined by the Charlson Comorbidity Index. STATA 14 was used for analysis. There were a total of 151,380 patients undergoing ERCP that met the inclusion criteria, of which 20,045 (13.24%) were obese, 3,140 (2.07%) were overweight, and 128,470 (84.87%) were normal weight. Compared with normal-weight patients, patients with obesity were younger, more likely to be female, with a higher rate of choledocholithiasis and a lower Charlson Comorbidity Index (Table 1). The adjusted odds ratio (aOR) of mortality was 0.63 (95% CI, 0.30-1.36) for overweight, 1.00 (95% CI, 0.72-1.41) for obesity (all grades combined), 0.62 (95% CI, 0.29-1.29) for grade 1 obesity, and 1.49 (95% CI, 1.01-2.19) for grade 3 obesity. There was a mortality benefit in grade 2 obesity [0.13% vs 1.44%, aOR: 0.13 (95% CI, 0.02-0.93)], however, the mortality was not statistically different [0.34% vs 0.33%, aOR: 3.20 (95% CI, 0.33-31.33)] in the restricted analysis. Grade 3 obesity was associated with significantly higher mortality compared to patients with normal weight. There is no obesity paradox in hospitalized patients undergoing ERCP. The observed mortality benefit in grade 2 obesity was not present in the restricted analysis while excluding potential confounders like smoking and other chronic wasting conditions such as CKD in which patients tend to lose weight as the disease progresses.View Large Image Figure ViewerDownload Hi-res image Download (PPT)