Endoscopic Retrograde Cholangiopancreatography (ERCP) is a key therapeutic procedure in gallstone disease. Outpatient ERCP may reduce inpatient pressures and costs, but patient selection is challenging due to post-procedure complications. No validated criteria currently guide suitability for outpatient ERCP. This study aimed to identify factors associated with inpatient versus outpatient ERCP and to determine patient characteristics predictive of post-ERCP complications.

A retrospective cohort study included demographic variables, comorbidities, Clinical Frailty Scale (CFS), ASA classification, presenting diagnosis, and biochemical markers, including initial and peak bilirubin. Logistic regression assessed factors associated with inpatient ERCP; variables with p<0.10 on univariate analysis were included in multivariate models. ERCP-related complications were recorded, and univariate and multivariate regression analyses identified predictors of complications. Predictive performance was evaluated using Receiver Operating Characteristic (ROC) curves and reported as area under the curve (AUC).

Over a one-year period, 112 patients met inclusion criteria, with 67% undergoing outpatient ERCP. On univariate analysis, elevated initial and peak bilirubin levels, ASA grade, and a diagnosis of ascending cholangitis were significantly associated with inpatient ERCP (p<0.05). Following multivariate adjustment, none of these factors remained statistically significant (all p>0.05), indicating the absence of independent predictors for the choice of inpatient versus outpatient ERCP. Post-ERCP complications were observed more frequently in the outpatient cohort. Multivariate analysis identified age, Clinical Frailty Scale, ASA grade, and initial bilirubin as independent predictors of complications. ROC analysis demonstrated limited discriminative performance, with AUC ≤0.65; age and initial bilirubin had the highest predictive accuracy, though discrimination remained poor to fair.

In conclusion, there were no specific patient characteristics which correlated with the setting of ERCPs (inpatient vs outpatient). Initial bilirubin level, age, ASA and frailty were predictors of post-ERCP complications. Complications occurred more frequently in our outpatient setting, suggesting that a guideline for patient selection could be useful in deciding who is safe for an outpatient ERCP. Further work on a larger scale is required to establish a set criteria for patients who are best suited to outpatient ERCP.