Evaluation of the usefulness of cystic duct three-dimensional computed tomography with non-contrast for before laparoscopic cholecystectomy and endoscopic transpapillary gallbladder drainage in comparison to magnetic resonance cholangiopancreatography.

Introduction: The purpose of this study is to evaluate whether anatomical variations of the cystic duct and accessory bile duct can be grasped by cystic duct three-dimensional (3D)-computed tomography (CT) using non-contrast CT and to examine the possibility of omitting magnetic resonance cholangiopancreatography (MRCP).

Methods: Of patients who underwent non-contrast abdominal CT between May and October 2019, those who underwent MRCP within 1 month before and afterwards were targeted. Seven assessors visually evaluated the cystic duct 3D-CT images on a 5-point scale. Average scores of ≥3 and <3 points were assigned as the good and poor groups, respectively. Regions of interest (ROIs) were placed inside the cystic duct and four places around it, and the CT values in those ROIs were measured. The CT value difference was calculated by subtracting the surrounding CT values from the CT value in the cystic duct and converting the result to an absolute value. The CT value difference was classified into good and poor groups, and statistical analysis was performed. Seven assessors evaluated anatomical variations of the cystic duct and the presence of the accessory bile duct. The results were compared with the MRCP interpretation results to calculate sensitivity, specificity, positive predictive value, and negative predictive value.

Results: The average visual evaluation score was 3.8. The good and poor groups were comprised by 53 (85.5%) and 9 (14.5%) patients, respectively. The CT difference value averages were 54.7 and 15.9 for the good and poor groups, respectively, and the value was significantly higher in the good group (p = 0.001). The comparison results with MRCP were sensitivity=83.3%, specificity=78.0%, positive predictive value=47.6%, and negative predictive value=95.1%.

Conclusion: Cystic duct 3D-CT using non-contrast CT is a useful technique for understanding anatomical variations of the cystic duct and accessory bile duct. Our method may reduce the number of MRCP sessions performed.