Editing Retroperitoneum (section)

=== Duodenum ===
* 20-25 cm in length
* May be mobilized medially using a Kocher maneuver to expose these right-sided retroperitoneal structures
* '''Can be divided into 4 distinct parts:'''
*# '''First (superior) portion'''
*#* '''Intraperitoneal'''
*#* Extends from the pylorus to the neck of the gallbladder
*# '''Second (descending) portion'''
*#* '''Retroperitoneal'''
*#* '''Critically important to the urologist because of its proximity to the right renal hilum'''
*#* '''The common bile duct and the main pancreatic duct combine to enter the 2nd portion at the ampulla of Vater (hepatopancreatic ampulla).'''
*# '''Third (horizontal or inferior) portion'''
*#* '''Retroperitoneal'''
*#* '''Crosses the body from right to left and lies posterior to the SMA and anterior to the aorta'''
*# '''Fourth (ascending) portion'''
*#* '''Intraperitoneal'''
*#* Ascends and becomes intraperitoneal as it transitions into the jejunum