Scan Planes n Upper abdominal transverse scan (to demonstrate the left lobe of the liver, see p. 22)

n Right subcostal oblique scan (see p. 22) n High and extended right intercostal scans (see pp. 33 and 24) n Paramedian upper abdominal longitudinal scans (see p. 24)

n The liver exhibits a diaphragmatic surface and a visceral surface. n Both surfaces meet anteroinferiorly at the sharp inferior hepatic border and posterosuperiorly at the fixed part of the diaphragm. n The liver is divided anatomically into the right and left lobes, the falciform ligament separating the larger right lobe from the smaller left lobe. The quadrate lobe (segment IV) and the caudate lobe (segment I) belong physiologically to the left lobe (Figs. 318 and 319).

Fig. 318 Segmental anatomy of the liver, diaphragmatic surface. A line between the gallbladder and inferior vena cava divides the liver into right (Segment V-VIII) and left physiologic lobes (Segment I-IV)

Fig. 319 Segmental anatomy of the liver, visceral surface. Boundaries of the caudate lobe: upper hepatic border, falciform ligament, portal vein, and vena cava. Boundaries of the quadrate lobe: lower hepatic border, falciform ligament, gallbladder, and portal vein

Diaphragmatic Surface Liver

n Normal values: craniocaudal liver diameter on the midclavicular line (MCL) in heavy-set patients < 120 mm, in asthenic patients < 140 mm. Sum of length plus depth < 24-26 mm. Depth over the aorta at the level of the celiac trunk < 40 mm.

n Transducer: 2.5-5.0 MHz (depending on the abdominal circumference) n Right subcostal oblique scan: Ask the patient to take a deep breath and hold it. Define the dome of the liver with the diaphragm, hepatic veins, portal venous branches (common hepatic duct), the intrahepatic bile ducts, the gallbladder, and the hepatic parenchyma (see Fig. 320).

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Fig. 320a-d Subcostal oblique scans. a, c Scan through the porta hepatis into the upper part of the liver. PV = right and left branch of the portal vein. V = inferior vena cava, arrow = ligamentum venosum. b, d Scan directed from the inferior hepatic border (at top of image) to the fixed part (at bottom of image) demonstrates the quadrate lobe (QL) and caudate lobe (CL) anterior to the vena cava (VC). L = right lobe of liver, PV = portal vein n Scan through all portions of the liver in a fan-shaped pattern. n Upper abdominal longitudinal and intercostal scans: Evaluate the porta hepatis, the bile ducts, the portal vein, and the lateral portions of the liver (see Fig. 321). n Scanning tip: When examination conditions are not ideal, these same planes can be used for scanning the other portions of the liver and the gallbladder.

Fig. 321a-d a, b Upper abdominal longitudinal scan of the subdiaphragmatic vena cava and the termination of the hepatic veins (arrow). QL = quadrate lobe, PV = portal vein, CL = caudate lobe, VC = inferior vena cava, L = liver. c, d High intercostal scan on the right side demonstrates the costophrenic angle (CA), posterior portions of the diaphragm (DIA) and the entry echo of the lung (L)

n Changes in the liver: Sonographic abnormalities of the liver may consist of diffuse or circumscribed changes in the normal hepatic architecture:

• Diffuse changes (see Table 41, p. 234): These refer to a general alteration of normal liver architecture with regard to size, echogenicity, contours, vasculature, and tubular tracts. Changes in echo texture and contours are particularly significant.

• Circumscribed changes (see Table 44, p. 241): focal alterations in the normal echo texture of the liver. Their detectability depends on the difference in acoustic impedance between the change and normal surrounding liver (anechoic lesions such as cysts are easily recognized). A lesion that is isoechoic to surrounding liver can be distinguished only by the presence of a hypoechoic rim or vascular displacement n Changes in the portal veins (see Table 45, p. 257): Abnormalities of the portal vein and its tributaries may produce changes identical to those found in the systemic veins (see Table 34, p. 208).

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