The application of negative helical CT cholangiography in patients with obstructive biliary diseases

Objective: To evaluate the diagnostic value of negative helical CT cholangiography (N-CTC) in patients with obstructive biliary diseases. Methods: Sixty-eight cases with obstructive extrahepatic bile duct diseases which previously received B-mode ultrasound underwent helical CT enhancing scans with non-ionic contrast media. The raw data of scanning were first reformatted to bring out axial source images (ASI) and then minimum intensity projection (MinIP) and surface shadow display (SSD) images were obtained by editing ASI on the workstation. By blind method, 3 senile radiologists made the diagnoses in both obstructive location and naturally based on MinIP, SSD images, and ASI. The results were further compared with clinical diagnoses or surgical findings and pathology. Results: Among 68 cases, 25 cases got through the examination by 1 breath-hold, 43 cases finished it by 2 breath-holds. Compared to clinical diagnoses or surgical findings and pathology, the accuracy of MinIP, SSD images, and ASI in detecting obstructive location was 100.0%, 100.0%, and 98.5%, respectively. There was no significant difference between N-CTC and ASI (x2 = 0, P > 0.05). The whole accuracy of identifying obstructive nature with three sorts of modalities was 82.4%, 79.4%, and 92.6%, respectively. there was no significant difference between MinIP and ASI (x2 = 3.27, P > 0.05), but significant difference presented between SSD and ASI (x2 = 4.92, P < 0.05), and the total accuracy of MinIP and SSD images combined with ASI was 95.6%. Conclusion: As one of less-injury and easy examination methods, N-CTC had high accuracy in identifying obstructive location and its nature. Meanwhile, the combination of three kinds of imaging modalities could get accurate diagnoses in majority of cases