Correlation of common bile duct diameter by ultrasound and cholangiography

Common bile duct (CBD) diameter is often measured during ultrasound (U/S) of the liver and biliary tree. However, to date, no study has directly compared the measurements obtained during U/S to those obtained at ERC. Objectives: (I) To assess the degree of correlation between CBD diameter as measured at U/S and ERC, and (2) to see if that correlation was affected by bile duct diameter or cholangiographic findings. Methods: Patients whose CBD was measured by U/S and ERC within a 24 hour period were evaluated. No patient had any additional intervention between the two measurements. Data included age, CBD diameter at U/S and ERC (magnification correction=0.7), and findings at cholangiography. Comparisons were made using Pearson Correlation Coefficients (PCC). Results: 43 patients with a mean age of 52.4 years were studied; 70% were female. 21 patients had abnormal cholangiograms (11 strictures, 5 choledocholithiasis, 4 non-specific CBD dilation, and 1 leak). Overall mean CBD diameter was 7.4 mm by U/S and 8.1 mm by ERC (PCC=.69, p=.0001 ). In the group with normal cholangiograms, the mean CBD diameter was 5.0 mm at U/S and 6.0 mm by ERC (PCC=.66, p=.001). For those with abnormal cholangiograms, mean CBD diameter was 9.6 mm by U/S and 10.0 mm by ERC (PCC=.57, p=.006). Eighteen patients had a CBD diameter at U/S of <6.0 mm. Of these, 5 (28%) had abnormal cholangiograms, and the PCC for U/S and ERC measurements fell to 35 (p>.05). Patient Population CBD at U/S (mean) CBD at ERC (mean) PCC p-value All 7.4mm 8.1 mm .69 .0001 Normal Cholangio 5.0 mm 6.0 mm .66 .001 Abnormal Cholangio 9.6 mm 10.0 mm .57 .006 CBD ≥6.0 mm at U/S 10.2 mm 9.9 mm .55 .005 CBD <6.0 mm at U/S 3.7 mm 5.6 mm .35 .15 Conclusions: (1) Measurements of CBD diameter by U/S and ERC show good correlation overall, (2) this correlation is maintained in patients with both normal and abnormal cholangiograms, (3) 28% of patients with a CBD diameter <6.0 mm at U/S had abnormal cholangiograms, and (4) there is poor correlation between U/S and ERC in the measurement of CBD diameter in patients whose CBD diameter is <6.0 mm at U/S.

Duke Scholars

Author Jane Elizabeth Onken Medicine, Gastroenterology