Journal of Ultrasound in Medicine, Vol 10, Issue 12 653-657, Copyright © 1991 by American Institute of Ultrasound in Medicine
Contrast cholangiography versus ultrasonographic measurement of the "extrahepatic" bile duct: a two-fold discrepancy revisited
R. P. Davies, P. R. Downey, W. R. Moore, P. L. Jeans and J. Toouli
Department of Radiology, Flinders Medical Centre, Bedford Park, South Australia.
The upper limit of the normal extrahepatic duct diameter when measured by
sonography in our institution is less than half that when measured by
endoscopic retrograde cholangiopancreatography (ERCP). The objective of
this study was to locate possible sources of this discrepancy by comparing
measurements obtained on the same patient by sonography, before and after
ERCP. Thirty consecutive patients referred for ERCP were entered into a
prospective trial; bile duct measurements were obtained independently by
both techniques in 19 patients. Correcting for radiographic magnification,
the ERCP measurement was more than twice that obtained by ultrasonography.
Among the possible reasons for diverse results that we considered,
radiographic magnification, ultrasonic underestimation, and distending
effects of retrograde cholangiography (ERCP) were not found to be prominent
causes for the marked discrepancy that we observed. The most likely
explanation is that the duct in individual patients was being measured at a
different level by the two techniques. A retrospective comparison of the
studies obtained by each method suggests that the sonographic measurement
is most often of the right hepatic duct. If this is the case, the two
measurements show no statistically significant difference (P greater than
0.05). A prospective trial is needed to test this hypothesis.
