Clearly demonstrate the relationships of the aorta and vena cava to the diaphragm, liver, and gastric cardia.
Clearly define the aortic branches and vena cava tributaries and their course.
The vessels of the retroperitoneum are easily to identify with ultrasound, making them useful landmarks for scanning. You should make an effort to become familiar with them.
Relationship of the aorta and vena cava to the diaphragm, liver, and cardia
Position the transducer for an upper abdominal transverse scan and identify the liver, which at this level is interposed between the aorta and vena cava. The cardioesophageal junction lies anterior to the aorta. The hypoechoic musculature of the diaphragm is also seen (Fig. 3.26a). Rotate the transducer to a longitudinal plane and scan through the region. Identify the vena cava (Fig. 3.26b), the caudate lobe of the liver (Fig. 3.26c), the aorta, and the gastric cardia lying anterior to it (Fig. 3.26d). (The caudate lobe is described in detail on p. 67ff. and the gastroesophageal junction on p. 166ff.)
Area surrounding the celiac trunk and the course of the hepatic artery, splenic artery, and left gastric artery
The common hepatic artery curves upward and to the right from the celiac trunk to the porta hepatis, where it is accompanied by the portal vein and bile duct. The splenic artery turns to the left and runs with the splenic vein to the hilum of the spleen. This artery takes a very tortuous course. The left gastric artery passes upward from the celiac trunk and usually can be traced only a short distance (Figs. 3.27, 3.28).
Demonstrating the splenic artery, hepatic artery, and left gastric artery in longitudinal section
Sometimes you will see a phenomenon in longitudinal scans that may be somewhat confusing at first. It occurs when the scan simultaneously cuts the origin of the celiac trunk and the splenic artery anterior to it (Fig. 3.29a). Figure 3.29b explains this phenomenon.
Place the transducer longitudinally over the aorta, obtaining a sectional view of the celiac trunk (Fig. 3.30a,b). Mentally picture the splenic artery coursing behind the image plane. Now slide the transducer slowly to the left and follow the section of the splenic artery as it moves across the field of view (Fig. 3.30c–e).
Bring the transducer back to its original position (Fig. 3.31a) and then move it slowly to the right (Fig. 3.31b–d). Observe the section of the hepatic artery, which is shown schematically in Fig. 3.31e.
Demonstrating the hepatic artery and splenic artery in transverse section
The down-curved portions of the hepatic artery and splenic artery may occasionally cause peculiar imaging phenomena that are confusing initially. Refer back to Fig. 3.27. Both vessels show a marked downward curve as they leave the celiac trunk. Because of this, each artery may be cut twice in the same transverse plane—once at the origin and once in the periphery (Fig. 3.32). Figure 3.33 shows the appearance of this phenomenon in actual images.
Superior mesenteric artery, splenic vein, and renal vessels
You are probably familiar with the frontal anatomy of these vessels. The splenic vein passes over the superior mesenteric artery. The renal vessels lie directly below the origin of the superior mesenteric artery. Their distance from the artery is variable, as is the course of the splenic vein (Fig. 3.34a). You may be less familiar with the cross-sectional anatomy of this region. Please note: the renal arteries are posterior and the renal veins are anterior. The left renal vein is physiologically compressed between the aorta and superior mesenteric artery and shows mild congestion on the left side, proximal to the compression site. The right renal artery compresses the vena cava from the posterior side (Fig. 3.34b). The diagram in Fig. 3.34c illustrates these relationships in a lateral oblique view.
Demonstrating the superior mesenteric artery, splenic vein, and renal vessels in transverse section
Position the transducer for an upper abdominal transverse scan and locate the superior mesenteric artery and the splenic vein, which overlies the artery anteriorly. Now scan caudad in parallel sections. With some luck (which you will need), you can identify the left renal vein (Fig. 3.35); it runs to the left between the aorta and the superior mesenteric artery. Typically this vein is narrowed beneath the superior mesenteric artery and then expands on the left side of the aorta. Scan down through this region, spacing the scans at small intervals. When you know what to look for, you can frequently identify the renal arteries.
In many cases you can trace the right renal vessels back to the kidney. Place the probe transversely to the right of the midline and image the vena cava (Fig. 3.36a). Starting from a plane above the level of the kidneys, slowly move the transducer caudad. If it is not hidden by bowel gas, you can recognize the termination of the large right renal vein (Fig. 3.36b). As you slide the transducer lower, the renal vein will appear to “detach” from the vena cava and move laterally toward the kidney. This occurs because the renal vein runs laterally downward at a slightly oblique angle. As the scan moves lower, the vein approaches the renal hilum (Fig. 3.36c). Usually the renal artery, which parallels the vein, will also come into view (Fig. 3.36d,e). An oblique scan parallel to the costal arch can define the full length of the renal vein (Fig. 3.36f). An analogous scanning technique on the left side is very rarely successful in defining the left renal vessels.