The duodenal bulb is the 1st or superior part of the duodenum, which is the most-proximal and located the closest to the stomach. This part 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 of the stomach; the liver and gallbladder lie anterior to it. The common bile duct and gastroduodenal artery run posterior to it.