This video explains the altered anatomy that is encountered after a Billroth II operation. In a Billroth II resection, the lower part of the stomach is ablated and a second resection line is made in the area of the upper duodenum.
Continuity is restored by pulling up a loop of jejunum, which is sutured laterally into the body of the stomach. This preserves access to the duodenum, and the major duodenal papilla located there can be reached endoscopically. The difficulty during ERCP is finding the luminal opening of the afferent loop and intubating it, in order to reach the major papilla from the retrograde direction.
In some cases, the afferent loop does not lie on the side of the lesser curvature, and the reconstruction is then rotated 180° — known as a “Mornean reconstruction.” At endoscopy, the loop lying on the side of the greater curvature then has to be intubated.
To prevent symptomatic biliary reflux, a surgical variant that is often used involves creating what is known as a “Braun anastomosis,” in which the loops of small bowel are additionally joined below the stomach.