Endoscopic retrograde cholangiopancreatography (ERCP) is the first-line procedure for choledocholithiasis treatment. However, it is associated with a 10% rate of adverse events. Spontaneous migration of common bile duct (CBD) stones occurs in 6-33% of choledocholithiasis cases, making ERCP avoidable. This study aimed to identify predictors of spontaneous CBD stones’ migration.

Retrospective study including patients diagnosed with choledocholithiasis and submitted to ERCP. Patients were divided into 2 groups considering spontaneous stone migration (i.e.: the absence of CBD stones on ERCP). Data on patients’ characteristics, imaging findings, biochemical analysis, and ERCP procedure were analyzed to identify predictors of spontaneous migration of CBD stones.

334 patients with a mean age of 71.7 years were included in the study: 76.6% without and 23.4% with spontaneous migration of CBD stones. Although some patients’ features (gender and clinical presentation), imaging findings (diameters of the largest stone and CBD), biochemical analysis (bilirubin levels at diagnosis and pre-ERCP), and ERCP procedure characteristics (time from diagnosis to ERCP) were different between groups, only three variables were defined as predictors: the absence of acute cholangitis, the largest stone diameter ≤5mm, and the bilirubin levels pre-ERCP ≤ 2mg/dL. When using those variables together there was a chance of 81-86% to correctly distinguishing patients with and without spontaneous CBD stone migration.

The size of the largest stone at diagnosis was validated as a predictor of CBD stones’ spontaneous migration. Furthermore, two new predictors were identified: bilirubin levels pre-ERCP ≤ 2 mg/dL, and no acute cholangitis at the clinical presentation of choledocholithiasis. EUS and ERCP in the same session should be considered in patients with factors predictive of stone migration, especially when combined, to minimize unnecessary ERCP and possible complications.