rel="nofollow" href="#ulink_b771bdc2-1c18-5385-a286-5a97cc99ef59">Video 1.4, the image plane across the pancreas is generally obtained through a sweeping motion. The first major gastric landmark is the origin of the celiac artery and SMA from the aorta (Figure 1.4). The superior mesenteric vein (SMV), portal vein, and splenic vein can be used as guides to go back and forth across the pancreas and in the process, the left adrenal, kidney, and spleen can be seen. The splenic artery runs roughly parallel to the splenic vein, but is generally tortuous.
Figure 1.4 Sagittal cross‐section of digital anatomy at the level of the gastroesophageal junction, similar to a view seen during linear array endoscopic ultrasound (EUS). The celiac and superior mesenteric arteries (SMA) are shown at their insertion into the aorta. The renal vein (RV) is shown adjacent to the SMA and the splenic vein is shown adjacent to the pancreas.
Normal EUS anatomy from the duodenum
Radial array orientation (Video 1.5)
The radial array EUS examination through the duodenum follows a constrained path, but the endoscope can be rotated to put various structures into the inferior aspect of the image plane, as shown in the models of the duodenum, pancreas (brown), portal and superior mesenteric veins (blue), aorta (red), and SMA (silver). There are many structures of interest in a rather small area, and most of the images obtained are from the posterior view, with the liver to the right and the pancreas to the left of the image screen. After leaving the pylorus, the pancreas can be oriented with the tail pointed either to the left or inferiorly, and the splenic vein runs in the same direction as the pancreas. Going through the duodenal bulb, the gastroduodenal artery (GDA) often appears. Without Doppler, the GDA can be confused with the common bile duct (CBD) since these structures are nearly parallel in orientation and are very close to each other. As the apex of the duodenal bulb is reached, the image plane captures a longitudinal view of the CBD and the portal vein. As the descending duodenum is reached, the bile duct is seen in cross‐section and the IVC comes into view. As the third part of the duodenum is reached, the image plane rotates in such a way as to give a longitudinal cut through the IVC and then passes underneath the junction of the SMA with the aorta. Branches of the SMV can be found and the renal vein is visible in the “armpit” formed at the insertion of the SMA into the aorta. A special area is then highlighted in Video 1.5. Models show how the gastroduodenal artery and the hepatic artery (in red) relate to the CBD (in orange).
Figure 1.5 shows a model with an image plane and Figure 1.6 shows the resultant planar anatomy, which forms the stack sign – a phenomenon in which the portal vein, CBD, and main pancreatic duct are captured in the same field.
Linear array orientation (Video 1.6)
The linear array exam of the duodenum is an excellent way to see the CBD and pancreatic head. The anatomy is difficult to understand since the endoscope image is tipped into the C‐sweep of the duodenum, and then the image plane is swept in various angles, resulting in a cross‐sectioning of the CBD and pancreatic duct (PD). The image planes employed can be appreciated from observing the models in the video. The cross‐sections obtained can be positioned to first give a longitudinal view of the CBD and both longitudinal views and cross‐sections of the portal vein and SMV.
Figure 1.5 Visible Human Model of an image plane that is in the location in which radial array endoscopic ultrasound (EUS) generates the “stack sign”, in which the portal vein, common bile duct (CBD), and pancreatic duct are in the same field. A probe in orange is shown going into the proximal duodenum. The superior mesenteric vein (SMV) is also shown.
Figure 1.6 The cross‐sectional anatomy within the plane shown in Figure 1.3. The common bile duct (CBD), pancreatic duct (PD), and portal vein are all in the same field (“stack sign”).
Figure 1.7 Visible Human Model with a plane that is in a location similar to what can be generated during linear array endoscopic ultrasound (EUS), showing the relative position of the gastroduodenal artery, pancreatic duct (PD), hepatic artery, and common bile duct (CBD).
As seen in the first part of Video 1.6, if the endoscope is in the second part of the duodenum, the bile duct goes to the ampulla away from the transducer and the liver is towards the transducer. If the endoscope is in the duodenal bulb, as shown in the second part of the video, the liver is away from the transducer.
The GDA drapes over the portal vein and can be found most readily using Doppler. Figure 1.7 shows a model and Figure 1.8 the resultant cross‐section where the GDA can be found.
Normal EUS anatomy from the rectum
Radial array orientation, male (Video 1.7)
Video 1.7 shows models of various male pelvic structures, starting with the rectum and sigmoid colon, the aorta, and the iliac arteries with internal and external branches. The SMA is included to show the anterior direction of the models. The prostate, bladder, coccyx, and sacrum are added sequentially. A second set of models is then shown which contains the rectum, sigmoid colon, prostate, bladder, coccyx, sacrum, external iliac arteries (red), veins (blue), as well as three‐dimensional models of the internal and external anal sphincters. The sphincters and sigmoid colon are then removed.
Planar anatomy in the radial array orientation from the male rectum is then shown, starting distally and moving proximally. The anal sphincters are labeled, followed by the prostate, urethra, levator ani, and coccyx. The sacrum and seminal vesicles are then shown, followed by the right internal iliac artery.
Figure 1.8 Cross‐sectional anatomy generated within the plane shown in Figure 1.5. The gastroduodenal artery (GDA) and common bile duct (CBD) are shown with the pancreatic head. The portal vein (PV) is shown near the portal confluence.
Radial array orientation, female (Video 1.8)