Bilirubin Correlation May Preclude MRCP in Acute Cholecystitis Patients With Normal Common Bile Duct Diameter

OBJECTIVE. In patients with acute cholecystitis (AC), accurate identification of a common bile duct (CBD) stone before cholecystectomy is of concern for surgeons, gastroenterologists, and radiologists. This study evaluates the utility of preoperative MRCP taking into consideration both sonographic findings and biochemical predictors for choledocholithiasis. MATERIALS AND METHODS. Fifty-seven patients (58% women; mean age, 54 years old) with signs of AC on right upper quadrant (RUQ) ultrasound (US) who underwent subsequent MRCP from 2007 to 2017 were identified using a text-based search and retrospectively analyzed, using ERCP as the reference standard. RESULTS. For patients with AC who had a normal CBD diameter on initial RUQ US, we found a significant difference in the total and direct bilirubin levels of patients who had positive (1.94 vs 4.02 mg/dL, respectively; p = 0.013) and negative (0.71 vs 2.13 mg/dL, respectively; p = 0.02) findings for CBD stone on MRCP. ROC curve analysis showed an increased total bilirubin threshold of > 2.3 mg/dL (standard threshold, 1.2 mg/dL), which yielded a negative predictive value (NPV) of 95%. An increased direct bilirubin threshold of > 0.9 mg/dL (standard threshold, 0.2 mg/dL) yielded an NPV of 100%. CONCLUSION. In patients with AC who have a normal CBD diameter on RUQ US, normal or even mildly elevated bilirubin levels below a calculated threshold may obviate preoperative MRCP. Radiologists should be active participants in clinical decision-making; discussion between referring physicians and radiologists regarding biochemical markers and sonographic findings will lead to more appropriate use of preoperative imaging.