Background and Study Aims: Animal studies suggest that placement of endobiliary stents wholly above the papilla (the "inside-stent") prolongs the duration of stent patency. We reviewed the cholangiographic characteristics of patients with malignant obstructive jaundice in order to evaluate the feasibility 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 undergone endoscopic retrograde cholangiopancreatography (ERCP) for malignant obstructive jaundice at our hospital, to determine the relative frequencies of the types of cancers. The ERCP films of 59 relevant consecutive patients with 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 jaundice were pancreatic cancer (57%), biliary cancer involving the hilum (19%, including metastatic disease), nonhilar biliary cancer (14%), and papillary 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 two-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 in the axis of the distal common bile duct. Conclusions: For most biliary cancers, the stricture is high enough to allow the placement of a stent fully above the papilla, but this is not possible for most pancreatic cancers (or any papillary cancers). An "inside-stent" approach would be possible in about one-third of patients with malignant obstructive jaundice if a clearance length of over 2 cm between the stricture 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 of the stent would approximate the average angulation in the axis of the common bile duct and help to prevent dislocation.
