Use of magnetic resonance cholangiography in the diagnosis of choledocholithiasis

Abstract

The diagnosis of choledocolithiasis is pivotal for therapeutic planning in patients with symptomatic gallbladder stones. The classically estimated prevalence of common bile duct (CBD) stones in patients who have undergone cholecystectomy for symptomatic cholelithiasis is estimated to 15% [1]. This prevalence is higher in elderly patients (15‐ 60%) than in patients younger than 60 years [2]. With the increased number of laparoscopic cholecystectomies, pre- or peroperative diagnosis of choledocolithiasis has become more critical. The diagnosis of CBD stones with noninvasive imaging remains a challenge. Transcutaneous sonography and unenhanced helical computed tomography (CT) have a sensitivity of 20 ‐ 80%, in diagnosing choledocolithiasis according to the literature. However, the specificity of sonography and CT is higher than 90% [3‐5]. From a practical point of view, when a CBD stone is detected by a noninvasive method, especially with CT, the positive predictive value is good enough for planning a surgical procedure that should include intraoperative cholangiography (IOC) and stone extraction, if necessary. When no stone is seen with sonography and/or CT, a more sensitive test, and usually a more invasive one, is required to definitively rule out a CBD stone. This assessment could be performed before surgery with either endoscopic retrograde cholangiography (ERC) or endoscopic ultrasonography (EUS). Systematically performed IOC could also replace preoperative evaluation according to surgical researchers. For a long time, ERC has been considered the diagnostic gold standard, with a sensitivity of 95% in detecting choledocolithiasis [6], even though it may miss small stones, especially when the CBD is dilated. EUS is the more accurate imaging test for evaluating extrahepatic bile ducts. EUS should be considered a minimally invasive procedure, with minimal morbidity and mortality (even duodenal perforation remains a rare but severe complication), but it requires general anesthesia and no previous gastric surgery. Moreover, it is a highly operator-dependant procedure, and it does not allow a therapeutic approach other than an endoscopic sphincterotomy. The limitations of these noninvasive an invasive procedures emphasize the need of a noninvasive reproducible imaging test with both a high accuracy for the diagnosis of choledocolithiasis and the ability to provide a preoperative mapping of the bile ducts. Magnetic resonance (MR) cholangiography has given radiologists the opportunity to display the biliary tract by combining the advantages of projectional and cross-sectional imaging.