Transient hepatic attenuation difference (THAD) in biliary duct disease.

Background: THADs are associated with a wide spectrum of hepato-biliary pathologies. The aim of this paper is to find out the role of THADs in the imaging assessment of biliary diseases. We performed a retrospective study to establish the frequency of arterial phenomena in patients with specific biliary diseases.
Methods: Out of 1833 patients who underwent upper abdomen biphasic CT (2003-2007), we selected those with the following diagnoses: biliary duct dilation due to extrahepatic obstruction (20 patients-group A), intrahepatic-hilar cholangiocellular-carcinoma (19 patients-group B), and cholangitis (14 patients-group C). THAD presence/pattern was assessed for each group. Patients without any demonstrable clinical/imaging signs of liver/biliary pathology (1124) were the control group.
Results: THADs were observed in 36/53 (67.9%) and 20/1124 (1.78%) in study and control groups respectively, with significant association between each diagnostic group and THAD patterns (P < 0.0001). Eleven out of 20 (55%) group A patients showed peribiliary-THAD around dilated biliary tracts; 15/19 (79%) group B patients demonstrated portal involvement and sectorial-THAD; 10/14 (71%) group C patients revealed polymorphous-THAD all along inflamed biliary duct.
Conclusions: However, THADs are complex phenomena, their evaluation can be an additional diagnostic tool in patients with a biliary pathology. Diffuse peribiliary, sectorial, and polymorphous-THADs show a good rate of correlation (P < 0.0001) with biliary duct ectasia, portal infiltration, and cholangitis, respectively.