Utilizing CT to identifyclinicallysignificant biliary dilatation in symptomatic post-cholecystectomy patients: when should we be worried?

Abstract

Todetermine a reliable threshold common ductdiameter on CT, in combination with other ancillary CT and clinical parameters, at which the likelihood of pathologyrequiring further imaging or interventionis increased in post-cholecystectomy patients. In this IRB approved retrospective study, two attending radiologists independentlyreviewed CT imagingfor118 post-cholecystectomypatients, who were subsequently evaluated with MRCP, ERCP, or EUS, prompted by findings on the CT and clinical status. Measurements of the common duct (CD) were obtainedat the porta hepatis, distal duct, and point of maximaldilationonaxial and coronalCT scans.Patients were grouped by whether theyrequired intervention after follow-up imaging. Pertinent baseline lab values and patient demographics were reviewed. Of the 118 post-cholecystectomy patients, 38 patients (31%) required intervention, and 80 patients (69%) did not require intervention after follow-up imaging. For both readers, axial and coronal CD diameters were significantlyhigher in the 'intervention required' vs 'no intervention'groups at all locations (p value < 0.05). There was good to excellent inter-reader agreement at all locations (ICC 0.68-0.92). Pertinent baseline lab values including AST (p = 0.043), ALT (p = 0.001), alkaline phosphatase (p = 0.0001), direct bilirubin (p = 0.011), total bilirubin (p = 0.028), and WBC (p = 0.043) were significantly higher in the 'intervention required' group. CD thresholds of 8mm yielded the highest sensitivities (76-95%), and CD thresholds of 12mm yielded the highest specificities (65-78%). CD combined with bilirubin levels increased sensitivity and specificity, compared to using either feature alone. Dilated CD on CT combined with bilirubin levels increases the sensitivity and specificity for identifying patients needing intervention. We recommend that a post-cholecystectomy patient who presents with a CD diameter > 10mm on CT and elevated bilirubin levels should undergo further clinical and imaging follow-up.