rel="nofollow" href="#ulink_e169e274-d283-5689-b97b-2d743a39368f">Figure 6.12). A normal caliber duct will appear as a small, sometimes difficult to see, echolucent dot in the middle of the pancreatic parenchyma. Rotation to the left at the level of the celiac axis and body of the pancreas brings into view the pancreatic neck with the portal vein confluence deep to it. The splenic vein merges into the confluence from the patient’s left and the superior mesenteric vein runs caudad from the portal vein confluence. A little further leftward rotation of the echoendoscope may produce views of the right border of the pancreatic neck looking down towards the pancreatic head. Sometimes, longitudinal views of the pancreatic duct can be obtained from this view.
Figure 6.3 Radial EUS: pancreas tail. PD, pancreatic duct; SA, splenic artery; SV, splenic vein.
Figure 6.4 Radial EUS: pancreas tail.
Figure 6.5 Radial EUS: pancreas neck. PD, pancreatic duct; PV, portal vein; SV, splenic vein.
Figure 6.6 Radial EUS: head of pancreas. DP, dorsal pancreas; VP, ventral pancreas.
Figure 6.7 Radial EUS: ampulla.
Figure 6.8 Radial EUS: head of pancreas. CBD, common bile duct; PD, pancreatic duct.
Figure 6.9 Radial EUS: head of pancreas, vasculature. CBD, common bile duct; PD, pancreatic duct; PV, portal vein; SMV, superior mesenteric vein; SV, splenic vein.
Figure 6.10 Radial EUS: head of pancreas. CBD, common bile duct; PD, pancreatic duct.
Figure 6.11 Linear EUS: pancreas body. PD, pancreatic duct; SA, splenic artery; SV, splenic vein.
Figure 6.12 Linear EUS: pancreas tail. PD, pancreatic duct; SV, splenic vein.
As with radial endosonography, the linear duodenum presents the endosonographer with the most variability in endosonographic relationships of vessels, ducts, and periduodenal organs. There is a marked transition in the direction of the scope tip and therefore anatomic views between entering the duodenal bulb in a “long position,” where the scope tip is pointing cephalad and posterior, and a “short position” when withdrawing from the second portion of the duodenum, where the scope tip is pointing caudad. Generally, we try to start by inserting the linear echoendoscope deep into the second portion of the duodenum. With the echoendoscope in a short position in the second portion of the duodenum, the scope is designed to be facing the medial wall of the duodenum near the region of the ampulla (Figure 6.13). On slightly rotating the scope right or left with very gentle withdrawal, usually the pancreatic duct will be seen first traveling relatively perpendicularly away from the transducer. The CBD will be seen to originate from the ampulla between the duodenal lumen and the pancreatic duct (Figure 6.14). The pancreatic parenchyma seen at the level of the ampulla represents primarily the ventral pancreas. The relative echolucency of the ventral anlage commonly seen by radial endosonography may be less apparent by linear endoscopic ultrasound (EUS). At this level, if vessels are seen deep to the pancreatic head they are usually the superior mesenteric vein and artery. If one inserts the echoendoscope deeper into the third portion of the duodenum, the uncinate portion of the pancreas nestled among the vessels of the mesenteric root may be seen. Because this is a difficult view to get with a radial instrument, this view using a linear instrument is sometimes the only way in which deep uncinate tumors may be seen. From the ampullary region, further gradual withdrawal and rotation to the left (counterclockwise) will follow the course of the tubular structures of the porta hepatis. The pancreatic head will appear as the tissue between the superior mesenteric vein/portal vein and the duodenal wall.
Figure 6.13 Linear EUS: ampulla.
Figure 6.14 Linear EUS: head of pancreas. CBD, common bile duct; PD, pancreatic duct.
Endosonographic appearance of the normal pancreatic parenchyma
There is considerable variability in the endosonographic appearance of the pancreatic parenchyma. Classically it has a homogeneous, fine, “salt and pepper” appearance with echogenicity similar to the spleen. The ventral anlage is more echolucent because of its different embryologic origin and its lesser content of echogenic fat. In the elderly, the pancreas can get more nodular with courser echogenicity. In obese patients, the pancreas becomes infiltrated with fat and can almost disappear into the retroperitoneal fat. Fortunately, any pathologic pancreatic lesions, such as dilated ducts, cysts, or neoplasms, will be easily visible in the bright background of retroperitoneal fat. Thin patients typically offer particularly detailed imaging of the pancreas.
Chapter video clips
Video 6.1 Linear array EUS head of pancreas.
Video 6.2 Linear array EUS of the pancreas neck to tail.
Video 6.3 Radial array EUS head of pancreas.
Video 6.4 Radial array EUS of the pancreatic neck to tail.
7 Liver, Spleen, and Kidneys: Radial and Linear
Nalini M. Guda1 and Marc F. Catalano2
