Acquired constricting and restricting lesions of the descending duodenum.

The descending duodenum is a structure with distinct pathologic processes and anatomic relationships that requires a systematic approach to the differential diagnosis. Because of its tubular shape and fixed position in the retroperitoneum, both intrinsic duodenal and juxtaduodenal diseases are capable of producing luminal narrowing and obstruction. Duodenal lesions may be located in the mucosa or submucosa. Extraduodenal lesions may originate in adjacent structures--such as the pancreas, liver, gallbladder, colon, and lymph nodes--or from other retroperitoneal structures. Causes of duodenal obstruction include intraluminal masses, such as bezoars; duodenal inflammation, such as as peptic ulcers and Crohn disease; hematomas; and benign or malignant mucosal and intramural tumors. Pancreatic inflammation; tumors; and extrinsic compression caused by gallbladder processes, hepatic masses, retroperitoneal fluid collections, and tumors, including lymphoma, may produce duodenal obstruction. Abdominal radiography, barium studies, multidetector computed tomography, magnetic resonance imaging, and positron emission tomography may be used to depict and characterize duodenal strictures. Integration of imaging, clinical, laboratory, and endoscopic findings plays a major role in establishing a diagnosis of obstructive duodenal strictures.