Common Bile Duct Stone Size Is an Independent Predictor of Stone Detection by Magnetic Resonance Imaging

Abstract

Introduction: Endoscopic retrograde pancreatography (ERCP) is now primarily considered a therapeutic modality for management of common bile duct (CBD) stones. Endoscopic ultrasound (EUS) and Magnetic resonance imaging (MRI) are less invasive modalities used in the diagnosis of CBD stones prior to ERCP. The aim of the study is to detect if there is an additional diagnostic yield of EUS over MRI in detecting small common bile stones. Methods: A retrospective cross-sectional study was performed in patients who underwent ERCP between July 2011 and March 2017 for suspected CBD stone. The study included patients with CBD stone confirmed on ERCP and had a MRCP and an EUS within 72 hours from ERCP. Patient's demographic data, medical/surgical history, and imaging findings were collected from electronic health record (EHR). Imaging findings included CBD stone size on ERCP (categorized as small ≤5 mm vs. large >5 mm), CBD diameter (categorized as dilated if CBD diameter >8 mm), and presence or absence of CBD stone on EUS and MRCP. Results: A total of 110 patients were identified to have CBD stone on ERCP. In the final analysis, there were 110 patients with MRCP detecting stone in 66.4% patients. Seventy-two (65.5%) patients had small CBD stone and 38 (34.5%) had large CBD stone. Of this study population, the median age was 53 years, and 61.8% were female. The median BMI was 28.5. A total of 41 (37.3%) had hypertension; 22 (19.8%) had hyperlipidemia and 16 (14.4%) had diabetes. Most patients had cholecystectomy (47.3%) after ERCP and 39.1% before ERCP while the rest still have their gallbladder. Sixty-one (55.4%) had dilated CBD (Table 1). The multivariate logistic regression analysis revealed that larger stone size was associated with a higher likelihood of stone detection by MRCP (adjusted odds ratio: 5.57; 95% confidence interval [CI] 1.66 -18.7; P=0.005) (Table 2).Table: Table. Study population characteristics based on CBD stone size (univariate analysis)Table: Table. Multivariate Logistic Regression Results for the CBD stone detection by MRCPConclusion: MRCP has lower detectability rate for small (≤ 5 mm) common bile duct stone compared to EUS and ERCP. Sensitivity of MRCP for stones larger than 5 mm was satisfactory. Patients with a low or intermediate clinical index of suspicion for choledocholithiasis, further investigation with EUS is recommended despite negative MRCP.