The incidence of acute pancreatitis has increased in recent decades.1, 2 Acute pancreatitis is an important cause of morbidity and mortality in Western countries, and it is one of the main causes of hospital admission for digestive reasons.3, 4 In most countries, acute pancreatitis is most frequently due to biliary etiology.5 Acute biliary pancreatitis (ABP) is produced by stones traveling from the gallbladder to the common bile duct (CBD). These stones can obstruct the passage of pancreatic juice, which then triggers pancreatitis.6

In one in five patients with ABP, persistent gallstones in the CBD are detected in imaging tests after the patient has presented in the emergency room. Among these patients, only one third experience spontaneous resolution.7 The presence of persistent choledocholithiasis (PC) can predispose to episodes of recurrent pain, acute cholangitis, and the recurrence of pancreatitis in the short term.8, 9

Magnetic resonance cholangiopancreatography (MRCP), endoscopic ultrasonography (EUS) or endoscopic retrograde cholangiopancreatography (ERCP) are the most common techniques for diagnosing PC as conventional abdominal ultrasonography has limited accuracy.10 However, those techniques are expensive, endoscopy is invasive, they can increase hospital stay and delay cholecystectom if performed on patients with a low probability of PC.11

Although non-invasive predictive models of PC (based on blood tests and ultrasound findings) have been published previously,10, 11, 12, 13 few have focused exclusively on patients with ABP. Most study populations included patients with biliary colic and acute cholangitis.14 Moreover, the pathophysiology of ABP differs from that of choledocholithiasis without pancreatitis.15 Therefore, the predictors of choledocholithiasis identified in those studies might have limited applicability to patients with ABP. On the other hand, studies that focused on patients with ABP exclusively have shown conflicting results.9, 16, 17

The present study aimed to identify a combination of epidemiological, analytical, and ultrasound variables that could predict the presence of PC in CBD, among patients with ABP.