Utility of MR cholangiography for follow-up examination after metallic stent placement in the bile duct

To evaluate the efficacy of MR cholangiography for follow-up examination after metallic stent placement in the bile duct. Between December 1999 and June 2000, 15 patients with biliary obstruction in whom metallic biliary stents had been placed underwent MR cholangiography during follow-up examination. The causes of obstruction were hilar cholangiocarcinoma (n=6), common bile duct cancer (n=5), gall bladder cancer (n=1) and pancreatic cancer (m=3). The types of self-expandable metallic stent employed were the nitinol stent (n=2), the endocoil nitinol stent (n=3), the ultraflexed diamond stent (n=5), and the wallstent (n=5). Using MR cholangiography, we measured the diameter of that part of the biliary stent which showed high signal intensity, assigning one point if this was less than one third of the stent diameter, two points of between one third and two thirds, and three points if more than two thirds. We decided that a higher score indicated fewer artifacts. The score was 1.7-3 (mean, 2.3) points for the endocoil nitinol stent, 1.7-2.3 (mean, 2) for the nitinol stent, and 1-3 (mean, 1.7) for the ultraflex diamond stent. In most cases, two thirds of the stent diameter was observed. For the wallstent, the score was 1-1.7 (mean, 1.3) points and the inner portion of the stent was almost invisible. MR cholangiography is not useful for follow-up examination after the placement of wallstents and three other types of nitinol stent in the bile duct