The duodenum is the first portion of the small intestine, extending from the pylorus of the stomach to the ligament of Treitz, where it transitions into the jejunum. It is shaped like the letter C and wraps around the head of the pancreas. On ultrasound, the duodenum is most commonly evaluated in the context of pyloric stenosis in infants, where thickening and lengthening of the pyloric muscle is measured, and in adults when searching for the cause of bile duct or pancreatic duct obstruction. The ampulla of Vater, where the common bile duct and pancreatic duct empty into the duodenum, is located in the second portion of the duodenum and can sometimes be visualized on ultrasound.
Sonography Term