Difference of CBD width on US vs. ERCP.

Purpose: To investigate the relationship between US and ERCP in the measurement of common bile duct (CBD) width after application of Compound and Harmonic imaging on ultrasound.

Methods: We prospectively evaluated the CBD width as measured on endoscopic retrograde cholangiopancreatography (ERCP) and ultrasonography (US), applying Compound and Harmonic US techniques, on 100 patients. Furthermore, we retrospectively re-examined US and ERCP images of 48 patients who underwent ERCP and US during the same hospitalization period.

Results: The average difference in measurements by US compared to ERCP was 2.3 mm (P < 0.01) in the retrospective and 1.9 mm in the prospective study (P < 0.001). The average difference in measurements between US and ERCP in post-cholecystectomy patients was 4.0 mm in the retrospective study (10 patients), and 3.8 in the prospective study (25 patients). The difference between the measurements on both examinations decreased with increasing CBD width. There was a good correlation between ERCP and US measurements of CBD width (r = 0.73 for all patients and r = 0.88 for patients with intact gallbladder, P < 0.001).

Conclusions: There is a gap between measurement of CBD width on US and ERCP of about 2 mm. The application of Compound and Harmonic techniques in the prospective study probably enabled a more accurate sonographic measurement.