The duodenal bulb (or the 1st / superior part of the duodenum) is short - only about 5 cm long.

• It lies anterolateral to the body of the L1 vertebra.

• The conical first 2 cm are mobile, attached to the hepatoduodenal ligament above and to the greater omentum below.  

• The distal 3 cm and the rest of the duodenum are secondarily retroperitoneal and immobile.

• The proximal part of the duodenal bulb ascends from the pylorus; the liver and gallbladder lie anterior to it.

• The common bile duct (CBD) and gastroduodenal artery run posterior to it.

Clinical significance

The duodenal bulb is the most frequent location of a peptic ulcer. An ulcer that penetrates the posterior wall of the duodenum can erode several important structures, including the gastroduodenal artery, as well as the structures within the hepatoduodenal ligament (portal triad = proper hepatic artery, common bile duct, and portal vein). Massive bleeding can result or perforation into the lesser sac (a relatively confined space), resulting in pancreatitis. Perforation of the anterior wall of the duodenum can result in gut contents spilling into the greater sac (larger part of the peritoneal cavity), causing generalized peritonitis. The gallbladder rests on the anterosuperior aspect of the duodenal bulb. Gallstones rarely may erode through the duodenal wall forming a fistula (connection) between the gallbladder and duodenum. If the stone is large enough, it may cause a small bowel obstruction distally at the ileocecal valve (gallstone ileus).