Helical CT in the examination of bile duct obstruction

Purpose: To assess the role of helical CT in the examination of cholestasis. Material and Methods: The US and CT reports of 36 consecutive patients with confirmed bile duct obstruction were evaluated in retrospect, the given diagnoses were compared with each other, and the final diagnoses confirmed by ERCP, surgery, fine needle or endoscopic biopsy, or autopsy. The bile duct was evaluated from helical 3-mm or 5-mm images reconstructed with 1-mm or 2-mm spacings, respectively, obtained after a bolus injection of 140 mi contrast medium containing 300 mg I/ml. Cross-section images and 2-D reformats displaying the extrahepatic bile duct in its full length were recorded for the interpretation. Results: An obstruction secondary to a choledochal gall stone was present in 14 patients, a tumoral obstruction in 18, a post-inflammatory stricture in 2, and chronic pancreatitis in one patient. In one patient the obstruction present at US was over at CT. A choledochal stone was correctly diagnosed at US in 14% and at CT in 71% of the cases. A correct tumor diagnosis was achieved in 28% and 44% of the cases, respectively. Benign and malignant bile duct wall involvement could not be reliably discriminated. The 2-D display was of significant value in assessing the nature and extent of the obstructive agent. Conclusion: Helical CT supplemented with 2-D reformats was a useful method in the cases of cholestasis where US failed to demonstrate the cause of obstruction. An impacted stone can be visualized with high confidence while a tumoral obstruction is to be suspected when the cause of blockage is not directly visible.