Figure 12a.  Gastric outlet obstruction preventing ERCP in a 56-year-old woman who presented with weight loss and intractable nausea and vomiting. (a) MR cholangiogram shows obstruction of the extrahepatic bile duct (straight arrow) secondary to lymphadenopathy. The scalloped appearance of the peritoneum (arrowheads) represents carcinomatosis. Gallbladder calculi are also seen (curved arrow). (b) MR cholangiogram of the stomach demonstrates marked antral wall thickening (arrows) secondary to adenocarcinoma, resulting in outlet obstruction.