Endoscopic ultrasound: Normal pancreaticobiliary anatomy
- Lyndon V Hernandez, MD, MPH
Lyndon V Hernandez, MD, MPH
- Clinical Associate Professor
- Medical College of Wisconsin
- Manoop S Bhutani, MD, FASGE, FACG, FACP
Manoop S Bhutani, MD, FASGE, FACG, FACP
- Professor of Medicine
- University of Texas MD Anderson Cancer Center
A major area of endosonographic diagnosis and intervention involves diseases of the pancreaticobiliary tract. A high degree of understanding of cross-sectional anatomy of the pancreaticobiliary tract is required to attain competence in this area [1,2]. Endoscopic ultrasound (EUS) provides high resolution images of the pancreatic duct as well as the parenchyma, and complements the ductal images seen in endoscopic retrograde cholangiopancreatography (ERCP).
This topic review will discuss normal pancreaticobiliary anatomy using radial scanning endoscopic ultrasound (EUS). The role of EUS in the evaluation of choledocholithiasis, pancreatic cancer, and chronic pancreatitis is discussed elsewhere. (See "Endoscopic ultrasound in patients with suspected choledocholithiasis" and "Endoscopic ultrasound in the staging of exocrine pancreatic cancer" and "Endoscopic ultrasound in chronic pancreatitis".)
EUS examination resembles standard endoscopy of the upper gastrointestinal tract. The operator performs the procedure while the patient is in left lateral decubitus position. Echoendoscopes are usually side-viewing and have an ultrasound transducer located at its tip that emits high frequency acoustic waves to the surrounding tissues. The latter permits the acquisition of unique "real-time" views of the gut wall and the surrounding organs and blood vessels.
Radial scanning EUS uses a scanning plane perpendicular to the axis of the echoendoscope (figure 1). The image is similar to that of computed tomography (CT) scan; if the patient is supine, the view is up from the feet. As a general rule, the upper part of the screen is anterior, and the right part of the screen is to the patient's left side. EUS depends upon a thorough knowledge of structures visualized in relation to the various transducer positions in the gastrointestinal tract (table 1).
EUS examination of the pancreaticobiliary tract can be performed by using one of two approaches: starting with transgastric sonographic views and then proceeding transduodenally, or vice versa. The transgastric approach provides images of the pancreatic body and tail, whereas the transduodenal approach allows imaging of the pancreatic head. It is important to understand that normal pancreaticobiliary anatomy with either of these approaches can be variable and is by no means exactly reproducible in every patient.
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