Mr cholangiography with volume rendering: receiver operating characteristic curve analysis in patients with choledocholithiasis

Biliary anatomy on 3D MRCP: Comparison of volume-rendering and maximum-intensity-projection algorithms

PURPOSE

To compare volume-rendering (VR) and maximum-intensity-projection (MIP) of three-dimensional T2-weighted turbo spin-echo magnetic resonance cholangiopancreatography using a free-breathing navigator-triggered prospective acquisition correction (3D-TSE-PACE-MRCP) to define biliary anatomies.

MATERIALS AND METHODS

VR and MIP images of 3D-TSE-PACE-MRCP for 102 patients were retrospectively evaluated. Interpretation of cystic duct variation and biliary branching patterns of each image were recorded independently by two radiologists in a blinded fashion. Interpretation confidence on a five-point scale was compared using the Wilcoxon signed-rank test. The McNemar test was used to compare the accuracies of each reformation with the reference standard obtained by consensus interpretation of both the images and source images.

RESULTS

The reference standard identified all biliary bifurcations and 95 of 102 cystic duct confluences (93.1%). VR findings agreed with the reference standard findings more often than MIP with regard to cystic duct variation (94 [92.2%] vs. 76 [74.5%], P<0.01) while there was no significant difference for biliary branching patterns (99 [97.1%] vs. 92 [90.2%], P=0.092). The mean confidence score was significantly higher with VR than MIP with regard to both cystic duct variation and biliary branching patterns (3.7 vs. 2.4; P<0.01; 4.1 vs. 3.3; P<0.01).

CONCLUSION

VR reformation of 3D-TSE-PACE-MRCP defines biliary anatomies more accurately than MIP.

[Acute cholangitis: imaging diagnosis and management]

Cholangitis is an infection of the biliary ductal system that results from biliary obstruction. Choledocholithiasis has been the leading cause of acute cholangitis. Acute cholangitis remains a life-threatening complication of biliary obstruction that needs emergency diagnosis and treatment. Ultrasound (US) is the primary imaging modality for assessment of patients with suspected acute cholangitis. US is both sensitive and specific in demonstrating biliary dilatation. However, biliary dilatation is not always present at the early stage of bile duct obstruction and the performance of US in demonstrating choledocholithiasis is poor. Computed tomography (CT) without contrast injection is more sensitive than US in demonstrating choledocholithiasis. Magnetic resonance cholangiopancreatography (MRCP) and endoscopic sonography (EUS) are the most sensitive techniques to correctly determine the underlying cause and level of biliary obstruction in patients with acute cholangitis. In patients without previous cholecystectomy, clinical, biological, and US results allow to determine patients with high probability of having choledocholithiasis even if the stone is not directly visible on US. Patients undergoing cholecystectomy require laparoscopic common bile duct exploration, especially if the common bile duct clearance is not checked before surgery by MRCP or EUS.

The role of magnetic resonance cholangiopancreatography in patients with suspected biliary obstruction

Endoscopic retrograde cholangiopancreatography (ERCP) is an accepted and accurate procedure that combines the advantage of diagnosis of biliary obstruction with possible therapeutic endobiliary intervention. However, it is an operator-dependent and invasive procedure that is associated with complications and limitations. Magnetic resonance cholangiopancreatography (MRCP) is a unique noninvasive technique for the diagnosis of biliary obstruction. It is well suited to provide the information required to plan the optimal therapeutic approach for these patients. MRCP has the potential to replace or at least precede ERCP as the first-line imaging effort in the evaluation of suspected biliary obstruction. Significant advantages and some notable limitations inherent to the modality dictate its judicious use in appropriate circumstances. The present article reviews the utility of MRCP in evaluation of biliary obstruction, with brief reference to its principles and techniques.