The Clinical Significance of Intraductal Ultrasonography (IDUS) for Patients with Suspected Common Bile Duct Stones

Abstract

Background & Aim: Although the utility of intraductal ultrasonography (IDUS) for common bile duct stones has been reported, the clinical significance of this procedure in making therapeutic decisions has not been well clarified. In conjunction with the diagnostic accuracy of ERCP in patients with common bile duct stones, we investigated the optimal application of IDUS for suspected such stones. Methods: Between May 2005 and November 2006, 215 patients (mean age, 72.0; range, 30-94 years; male, 117; female, 98) who were suspected of having common bile duct stones based on findings of blood tests or clinical imaging were enrolled in this study. When a bile duct stone was not depicted by ERCP, transpapillary IDUS was carried out by inserting an IDUS probe with a frequency of 20 MHz (UM-G20-29R: Olympus Optical Co., Tokyo, Japan) into the bile duct. Endoscopic sphincterotomy (EST) and stone removal were performed when a diagnosis of bile duct stones was made. The diagnostic accuracy of ERCP for bile duct stones, and the maximum size of the stones (S), the diameter of the bile duct (BD), and its ratio (S/BD) in the E group (ERCP revealed the stones) and the I group (only IDUS depicted the stones) were evaluated. Results: ERCP revealed bile duct stones in 170 patients. In the remaining 45 patients who underwent IDUS, bile duct stones and sludge were demonstrated in 12 patients and 4 patients, respectively. EST and stone removal were performed in the 182 patients with bile duct stones. No symptoms were observed in 29 patients without stones at follow-up (mean duration, 7.5 months; range, 1.1-17.9 months). The sensitivity, specificity and accuracy of ERCP for bile duct stones were 93.4%, 100.0%, and 94.4%, respectively. The mean size of stones in the E group was significantly larger than that in the I group (10.2 mm vs. 4.8 mm, P < 0.001). There was no significant difference in the diameter of the bile duct between the two groups (13.9 mm vs. 14.6 mm). The S/BD ratio in the E group was significantly higher than that in the I group (0.74 vs. 0.35, P < 0.001). The diagnostic accuracy of ERCP for bile duct stones 2-5 mm, 6-9 mm, and ≥10 mm in maximum size was 71.9%, 95.2%, and 100%, respectively (2-5 mm vs. ≥6 mm, P < 0.001). In the 32 patients whose stones were 2-5 mm in size, the diagnostic accuracy of ERCP with the bile duct having diameter of 5-9 mm, 10-14 mm, and ≥15 mm was 90.9%, 64.7%, and 50.0%, respectively. Conclusions: ERCP is very sensitive in detecting bile duct stones. However, IDUS is recommended when ERCP is not diagnostic in patients having a dilated bile duct with suspected bile duct stones because small stones may be missed.