INTRODUCTION

Performing endoscopic retrograde cholangiopancreatography (ERCP) in patients with Roux-en-Y anatomy poses a major challenge to gastrointestinal endoscopists. In the current era of the obesity epidemic, this situation is encountered with increasing frequency due to the popularity of Roux-en-Y gastric bypass (RYGB) surgery (figure 1) and the high prevalence of gallstone disease in these patients [1-3]. (See "Surgical management of severe obesity", section on 'Roux-en-Y gastric bypass'.)

Roux-en-Y anatomy may also result from:

• Gastric resection surgery (figure 2) (see "Invasive gastric cancer: Surgery and prognosis", section on 'Surgical treatment for localized disease')
• Pancreaticoduodenectomy (figure 3 and figure 4) (see "Pancreaticoduodenectomy (Whipple procedure): Techniques")
• Liver transplantation (see "Living donor liver transplantation", section on 'Surgical techniques and recipient outcomes')
• Other biliary tract surgeries, such as the repair of bile duct injuries or as part of the treatment of cholangiocarcinoma, resulting in the formation of a hepaticojejunostomy (figure 5) or choledochojejunostomy (see "Repair of common bile duct injuries", section on 'Repair options' and "Treatment of localized cholangiocarcinoma: Surgical management and adjuvant therapy", section on 'Surgical treatment and outcomes')

In patients with Roux-en-Y anatomy, it is frequently impossible to access the papilla (or bilioenteric/pancreatoenteric anastomosis) using a standard duodenoscope due to the length of bowel that must be traversed. For example, in the case of RYGB, an endoscope advanced through the "anatomic route" must traverse the esophagus, gastric pouch, and Roux limb (typically 100 to 150 cm in length), and then navigate the acute angle at the jejunojejunostomy into the biliopancreatic limb up to the papilla (an additional 80 to 100 cm). Moreover, in cases with a native papilla, the endoscopist is then faced with the challenge of cannulating the bile duct or pancreatic duct while approaching the papilla from a reverse position. (See "ERCP after Billroth II reconstruction", section on 'Cannulating the papilla from the reverse position'.)

To overcome these problems, non-standard approaches, innovative techniques, and specialized accessories have been developed to perform ERCP in patients with Roux-en-Y anatomy. Where available, percutaneous transhepatic cholangioscopy may be an option for patients in whom ERCP cannot be successfully performed. (See "Percutaneous transhepatic cholangioscopy".)