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tvpjournal.com | January/February 2016 | Today's VeTerinary PracTice imaging essenTiaLs Peer reviewed 111 Imaging Planes For each organ, the evaluation must use 2 different imaging planes, which is particularly true for any suspected abnormalities. The imaging planes used in organ evaluation may not align with standard imaging planes, such as sagittal, transverse, or dorsal planes. an oblique imaging plane is often used to best visualize an organ. make sure that all images are labeled appropriately, with correct orientation. These images will become an offcial part of the patient's medical record. TOUR OF THE ABDOMEN With the dog in dorsal or lateral recumbency, begin with the probe just caudal to the xiphoid process. Ultrasound of the Liver With a nondistance motion, angle the probe cranially. The midsection of the liver should come into view. depending on liver size, use a non- distance motion and angle the probe to the left to view the left side of the liver or the right to view the gallbladder and right side of the liver, including the porta hepatis (Figure 3). The normal liver has a coarse echogenicity and contains vessels: • The dominant vessels in the hepatic parenchyma are the portal veins, which have an outer hyperechoic wall due to the fibrofatty connective tissue surrounding the wall and within the wall itself. The intrahepatic portal veins are a continuation of the portal vein proper as it enters the porta hepatis. • The hepatic veins can be seen as hypoechoic tubular structures that do not have hyperechoic walls ( Figure 4); the vessels taper toward the periphery of the liver and enlarge centrally within the liver. The hepatic veins enter into the caudal vena cava in the dorsal right liver ( Figure 5). Figure 3. Long-axis image of the left side of the liver in a dog (A). Long-axis image of the right side of the liver and gallbladder in the same dog (B). Long-axis image of a bilobed gallbladder in a cat (normal anatomic variation of the gallbladder that can be seen in cats) ( C). A B C Figure 4. Short-axis (transverse imaging plane) view of the liver (right is to the viewer's left). The hepatic veins (arrow) are the hypoechoic vessels without a bright echogenic wall, whereas the portal veins (arrow head) are the hypoechoic vessels with a bright echogenic wall. i n the normal liver, portal veins usually dominate the landscape. Figure 5. Hepatic vein entering the caudal vena cava as it courses through the liver (quadrate lobe).