Experience with a catheter-based ultrasound probe in the bile duct and pancreas.
BACKGROUND AND STUDY AIMS: Complete examination of the biliary tree and pancreatic duct may be difficult or unsuccessful using conventional imaging instruments. The purpose of this study was to evaluate the cannulation success rate, clinical utility, and safety of a new catheter-based ultrasound probe (CBUSP) used in the biliary tree and pancreas. PATIENTS AND METHODS: The probes used in this study are manufactured by Microvasive (Watertown, MA, U.S.A.) and were 6.2 Fr in diameter, operated at 12.5 MHz. Thirty-six patients (11 with malignant bile-duct strictures, 12 with benign bile-duct strictures, two with bile duct stones, three with pancreatic duct strictures, one with a pancreatic cyst, one with pancreas divisum, three with sphincter of Oddi dysfunction, and three normal) underwent examination with a CBUSP. RESULTS: Cannulation was successful in all 36 patients. The hepatic artery and portal vein could be visualized with the probe in the proximal bile duct in 81% and 94% of the cases, respectively. The portal vein could not be adequately visualized in any patients when the probe was in the distal bile duct. The mean thickness of the normal bile duct wall was 0.17 cm, and the mean wall thicknesses proximal to a benign and malignant stricture were 0.16 and 0.17 cm, respectively. The mean thicknesses of benign and malignant biliary strictures were 0.32 cm and 0.31 cm, respectively (not significant). Eight of 12 benign biliary strictures (67%) and five of 11 malignant strictures (45%) were symmetrical. However, no obvious differences could be identified between benign and malignant biliary strictures. There were no catheter related complications. CONCLUSIONS: Further catheter modifications are needed, but it appears to be feasible to assess vascular invasion in cholangiocarcinoma and to characterize biliary strictures in a way that may be able to influence therapy options in some patients. The currently available CBUSP cannot distinguish between benign and malignant strictures. However, with technical modifications, this may be possible in the future. The clinical usefulness of CBUSP in the pancreas awaits further investigation, but pancreatic imaging is feasible.