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
1 University of Wisconsin, School of Medicine and Public Health, Pancreatobiliary Services, St. Luke’s Medical Center, Milwaukee, WI, USA
2 Medical College of Wisconsin, Pancreatobiliary Services, St. Luke’s Medical Center, Milwaukee, WI, USA
Introduction
This chapter describes the endosonographic features of the major organs of the abdomen: the liver, spleen, kidneys, and adrenal glands. Ultrasound features of the pancreas and bile duct are described elsewhere.
The liver, spleen, kidneys, and adrenal glands (left side) are visualized from the stomach (Videos 7.1 and 7.2).
Liver
Radial endosonography
As the radial probe is advanced through the esophagus into the gastric cardia, the liver is the predominant organ visualized. When positioning the abdominal aorta at the 6 o’clock position, the left lobe of the liver is seen anteriorly and medially to the right (Figure 7.1). The aorta, with a dark hypoechoic band which is the diaphragmatic crux, is seen immediately adjacent to the probe. In this position, near the hiatus, the hepatic veins are seen as anechoic structures, entering the inferior vena cava (IVC). In this position, possibly with left tip deflection, the spleen can be seen on the right of the screen. As the aorta is traced distally, maintaining its 6 o’clock position, the liver may still be seen anteriorly. Vascular structures can be differentiated from ductal structures by a thicker (echogenic) wall and the presence of flow.
When advancing the echoprobe towards the antrum, the gallbladder is often visualized as an oval‐shaped anechoic structure. In this position, the porta hepatis can be seen with subtle tip deflection upwards.
Linear endosonography
With the probe at the level of the diaphragmatic hiatus, the longitudinal aorta and celiac artery origin are the most recognizable reference points (Figure 7.2), demonstrated as tubular longitudinal structures. Here, rotation of the probe counterclockwise will bring into view the liver parenchyma and its vascular structures (Figure 7.3).
Advancing the probe at the level of the pylorus and duodenal bulb, clockwise rotation and superior tip deflection brings into view the porta hepatis along with several vascular structures. Use of Doppler can differentiate arterial from venous structures as well as biliary structures.
The entire liver is not visualized by endoscopic ultrasound (EUS). Despite this limitation, it is useful to carefully examine the liver since metastatic processes can be easily identified and biopsied and could lead to a change in clinical staging and management of a suspected tumor.
Spleen
The spleen appears as a homogeneous structure seen between the tail of the pancreas, left kidney, and gastric wall. With a radial scope it is imaged from the gastric cardia. It is similar to liver in echogenicity except that it is devoid of any ducts and vessels (Figure 7.4). It can be easier to follow the splenic vein after visualizing the pancreas from the gastroesophageal (GE) junction. The splenic artery, splenic vein, renal vein, and the left adrenal are usually visualized as well while attempting to scan the spleen. The splenic vein can be easily traced along the inferior aspect of the body and tail of the pancreas; however, the splenic artery is tortuous and it is difficult to follow its course to the celiac trunk. With a linear scope one has to scan inferior to the left kidney and laterally to visualize the spleen (Figure 7.5).
Kidney
Both