Accuracy and timeliness of an abbreviated emergency department MRCP protocol for choledocholithiasis

Purpose: To determine the diagnostic accuracy and time savings of an abbreviated magnetic resonance cholangiopancreatography (A-MRCP) protocol for detecting choledocholithiasis in patients visiting the emergency department (ED) for suspected biliary obstruction.

Methods and materials: This retrospective study evaluated adult patients (ages 18+ years) visiting an academic Level 1 trauma center between January 1, 2016, and December 31, 2017, who were imaged with MRCP for suspected biliary obstruction. Patients were scanned with either a four-sequence A-MRCP protocol or a conventional eight-sequence MRCP (C-MRCP) protocol. Image acquisition and MRI room time were compared. The radiology report was used to determine whether a study was limited by motion or prematurely aborted, as well as for the presence of pertinent biliary findings. Diagnostic accuracy of A-MRCP studies were compared with any available endoscopic retrograde cholangiopancreatography (ERCP) report within 30 days.

Results: One hundred sixteen patients met inclusion criteria; 85 were scanned with the A-MRCP protocol (45.9% male, mean 57.4 years) and 31 with the C-MRCP protocol (38.7% male, mean 58.3 years). Mean image acquisition time and MRI room time for the A-MRCP protocol were significantly lower compared to those for the C-MRCP protocol (16 and 34 min vs. 42 and 61 min, both p < 0.0001). Choledocholithiasis was seen in 23.5% of A-MRCP cases and 19.4% of C-MRCP cases. Non-biliary findings were common in both cohorts, comprising 56.5% of A-MRCP cases and 41.9% of C-MRCP cases. 44.7% of A-MRCP patients received subsequent (diagnostic or therapeutic) ERCP (mean follow-up time 3 days), in which A-MRCP accurately identified choledocholithiasis in 86.8% of cases, with sensitivity of 85%, specificity of 88.9%, positive predictive value (PPV) of 89.5%, and negative predictive value (NPV) of 84.2%. In comparison, 38.7% of C-MRCP patients underwent ERCP (mean follow-up of 2.3 days) with an accuracy of 91.7%, sensitivity of 80%, specificity of 100%, PPV of 100%, and NPV of 87.5%. Only 4.7% of A-MRCP exams demonstrated motion artifact vs. 12.9% of C-MRCP exams. One study was prematurely aborted due to patient discomfort in the A-MRCP cohort while no studies were terminated in the C-MRCP cohort.

Conclusion: An abbreviated MRCP protocol to evaluate for choledocholithiasis provides significant time savings and reduced motion artifact over the conventional MRCP protocol while providing similar diagnostic accuracy.