Feasibility of stent placement above the sphincter of Oddi ("inside-stent"') for patients with malignant biliary obstruction

Background and Study Aims: Animal studies suggest that placement of endobil iary stents wholly above the papilla (the "inside-stent") prolongs the dura tion of stent patency. We reviewed the cholangiographic characteristics of patients with malignant obstructive jaundice in order to evaluate the feasi bility of this approach and to assist in the design of a new stent. Patients and Methods: A review was conducted of 270 patients who had underg one endoscopic retrograde cholangiopancreatography (ERCP) for malignant obs tructive jaundice at our hospital, to determine the relative frequencies of the types of cancers. The ERCP films of 59 relevant consecutive patients w ith malignant obstructive jaundice were studied to determine the length of the stricture, the distance between the stricture and the papilla, and the angulation of the common duct. Results: The most frequent primary cancers causing malignant obstructive ja undice were pancreatic cancer (57%), biliary cancer involving the hilum (19 %, including metastatic disease), nonhilar biliary cancer (14%), and papill ary cancer (10%). The length between the lower end of the stricture and the sphincter was more than 2 cm for all hilar biliary cancer, representing tw o-thirds of nonhilar biliary cancer cases, while it was less than 1 cm for most pancreatic cancers. There was an average angulation of 30-40 degrees i n the axis of the distal common bile duct. Conclusions: For most biliary cancers, the stricture is high enough to allo w the placement of a stent fully above the papilla, but this is not possibl e for most pancreatic cancers (or any papillary cancers). An "inside-stent" approach would be possible in about one-third of patients with malignant o bstructive jaundice if a clearance length of over 2 cm between the strictur e and the sphincter is required, and in about 45% of patients if a minimum clearance of 1 cm is required. A 30-40 degrees flexion in the distal part o f the stent would approximate the average angulation in the axis of the com mon bile duct and help to prevent dislocation.