scanning planes is mandatory to cover all segments and the complete liver surface The patient should be examined from sub- and intercostally in the decubitus position as well in modified slightly oblique positions with the right arm above the head and the right leg stretched during all respiration cycles to identify the best approach and to avoid artifacts caused by the thorax. Examination in the standing position is additionally helpful due to its weight, the liver moves caudally by gravity, and scanning from sub- or intercostal probe positions according to the individual anatomy-avoides the interposed lung which is mainly true for the right posterolateral (superficial) parts of the liver using the intercostal approach. Other examination techniques have also been described but are not mentioned here in detail which might be additionally used a great number of variants of the normal has to be encountered -e.g. with respect to accessory lobules, vascular branching, shape and configuration Examination criteria An acronym has shown to be didactically helpful ["SSOTM] ·S=size o=outline T=texture measurement The size of the liver has been measured by many methods, including 3D-reconstructions. Liver size measurement has no impact in daily routine because there is no reliable and reproducible ultrasound method established so far sh normally described as pyramidal Outline The normal liver surface should be smooth with no lumps protruding or indentations The inferior liver border in the normal patient should have an acute angled edg Liver surface border delineation and other ultrasound criteria: Other ultrasound criteria are described in the respective chapters Texture, echogenicity The normal liver parenchyma is of medium homogenous echogenicity, usually slightly darker than the spleen and slightly brighter than the renal cortex independently of the age except in childhood [(32)]. It is essential when comparing the liver with the spleen and renal cortex that the comparison is done at the same depth. Liver surface and vessels borders are smooth and vascular architecture with its classic dichotomy in branching is percepted as a harmonic and detailed aspect. The image of the normal parenchyma varies very little among individual Liver veins The three liver veins are positioned in between the liver segments. Their course additionally to the Glisson's triad- is helpful in defining liver lobes and liver
scanning planes is mandatory to cover all segments and the complete liver surface. The patient should be examined from sub- and intercostally in the decubitus position as well in modified slightly oblique positions with the right arm above the head and the right leg stretched during all respiration cycles to identify the best approach and to avoid artifacts caused by the thorax. Examination in the standing position is additionally helpful due to its weight, the liver moves caudally by gravity, and scanning from sub- or intercostal probe positions – according to the individual anatomy - avoides the interposed lung which is mainly true for the right posterolateral (superficial) parts of the liver using the intercostal approach. Other examination techniques have also been described but are not mentioned here in detail which might be additionally used. A great number of variants of the normal has to be encountered – e.g. with respect to accessory lobules, vascular branching, shape and configuration. Examination criteria An acronym has shown to be didactically helpful [“SSOTM”]: • S = size • S = shape • O = outline • T = texture • M = measurement Size The size of the liver has been measured by many methods, including 3D-reconstructions. Liver size measurement has no impact in daily routine because there is no reliable and reproducible ultrasound method established so far. Shape Normally described as pyramidal. Outline The normal liver surface should be smooth with no lumps protruding or indentations. The inferior liver border in the normal patient should have an acute angled edge. Liver surface border delineation and other ultrasound criteria: Other ultrasound criteria are described in the respective chapters. Texture, echogenicity The normal liver parenchyma is of medium homogenous echogenicity, usually slightly darker than the spleen and slightly brighter than the renal cortex independently of the age except in childhood [(32)]. It is essential when comparing the liver with the spleen and renal cortex that the comparison is done at the same depth. Liver surface and vessels borders are smooth and vascular architecture with its classic dichotomy in branching is percepted as a harmonic and detailed aspect. The image of the normal parenchyma varies very little among individuals. Liver veins The three liver veins are positioned in between the liver segments. Their course - additionally to the Glisson`s triad - is helpful in defining liver lobes and liver
segments. Number and course of liver veins is somewhat variable [ Figure 1] Portal vein Formed by the confluens of the splenic and superior mesenteric vein, the portal vein be sonographically displayed using or less dicular to the lower costal margin(orientation might be achieved referring from the right shoulder to the umbilicus), preferably in a left decubitus position and in variably deep inspiration Intrahepatically, the portal vein bifurcates into a main left and right branch. The first (right) portal vein branch splits into an anterior and into a posterior branch, which itself leads to the segments V-VIIl. The latter(left) main portal branch bifurcates into segments II and Ill and, additionally, into the left medial branches for segments (caudate lobe), IVa and Ivb[Figure 2] He atc arter The common hepatic artery has its source from the celiac axis, branching into the gastroduodenal artery and into the proper hepatic artery(arteria hepatica propria) Anatomical variations are frequent (in up to 50 %) e.g. the origin of the left proper hepatic artery out of the left gastric artery as well as the variable arterial supply of the liver by superior mesenteric artery branches. The hepatic artery runs with the portal vein, the right main arterial branch frequently meandering around the portal vein sonographically displayed in short segments medially (or less often laterally) of the portal vein. The normal and pathological flow patterns are described below in the Doppler chapt Bile ducts Bile ducts accompany the portal vein and hepatic artery branches from the liver hilum into the liver lobules, intrahepatically forming the ductus principalis dexter and the ductus principalis sinister, which join as common bile duct( CBD). The extrahepatic course of the CBd is cranially (pre-pancreatic)often ventral to the portal vein and caudally(intrapancreatic) more dorsolateral. The respective course of the hepatic artery is more variable [ Figure 4 Figure 4 Common bile duct(CBD). The CBD, and therefore, the liver hilum, is often best examined in a left lateral decubitus position using a subcostal approach in slight inspiration [video]. In the typical view CBd (in between markers), portal vein (PV), hepatic artery(HA), inferior vena cava(IVC) and right renal artery(RRa) (and sometimes also the aorta [ Aod can be seen; the papilla region(PAP)is indicated Distanz a 054cn
segments. Number and course of liver veins is somewhat variable [Figure 1]. Portal vein Formed by the confluens of the splenic and superior mesenteric vein, the portal vein can be sonographically displayed using scans more or less perpendicular to the lower costal margin (orientation might be achieved referring from the right shoulder to the umbilicus), preferably in a left decubitus position and in variably deep inspiration. Intrahepatically, the portal vein bifurcates into a main left and right branch. The first (right) portal vein branch splits into an anterior and into a posterior branch, which itself leads to the segments V – VIII. The latter (left) main portal branch bifurcates into segments II and III and, additionally, into the left medial branches for segments I (caudate lobe), IVa and Ivb [Figure 2]. Hepatic artery The common hepatic artery has its source from the celiac axis, branching into the gastroduodenal artery and into the proper hepatic artery (arteria hepatica propria). Anatomical variations are frequent (in up to 50 %), e.g. the origin of the left proper hepatic artery out of the left gastric artery as well as the variable arterial supply of the liver by superior mesenteric artery branches. The hepatic artery runs with the portal vein, the right main arterial branch frequently meandering around the portal vein sonographically displayed in short segments medially (or less often laterally) of the portal vein. The normal and pathological flow patterns are described below in the Doppler chapter. Bile ducts Bile ducts accompany the portal vein and hepatic artery branches from the liver hilum into the liver lobules, intrahepatically forming the ductus principalis dexter and the ductus principalis sinister, which join as common bile duct (CBD). The extrahepatic course of the CBD is cranially (pre-pancreatic) often ventral to the portal vein and caudally (intrapancreatic) more dorsolateral. The respective course of the hepatic artery is more variable [Figure 4]. Figure 4 Common bile duct (CBD). The CBD, and therefore, the liver hilum, is often best examined in a left lateral decubitus position using a subcostal approach in slight inspiration [video]. In the typical view CBD (in between markers), portal vein (PV), hepatic artery (HA), inferior vena cava (IVC) and right renal artery (RRA) (and sometimes also the aorta [AO]) can be seen; the papilla region (PAP) is indicated
Liver pathology -diffuse liver disease Criteria for analysing diffuse liver disease include evaluation of liver parenchyma(echo texture, ultrasound attenuation, vascular architecture, etc.)as well as its surface (a high frequency transducer is helpful in detecting more details of the superficially located structures); liver hilum structures including perihepatic lymph nodes in the hepatoduodenal gament, lymph nodes in liver disease or neoplastic infiltration; analysis of hepatic vessel flow patterns using colour and pulsed wave Doppler imaging(CDi) Ultrasound contrast agents(USCA)have improved the detection/exclusion rate of focal liver lesions; in diffuse liver disease, USCA potential is much lower(e.g hepatic transit time Hepatic steatosis Hepatic steatosis is the most common liver pathology. Sensitivity and specificity of the detection of hepatic steatosis by B-mode ultrasound examination may be very high in the hands of an expert investigator who consistently applies specific criteria in patients with significant fatty liver disease. In transabdominal ultrasound, hepatic steatosis is characterised by increased echogenicity, which is often compared to the spleen or kidney parenchyma at the same depth [Figure 6]. Supporting findings may be ultrasound attenuation, which means a decrease in intensity as sound travels hrough a material, caused by absorption, scattering, and beam divergence Attenuation decreases detail analysis of vascular architecture, and it may cause a loss of visibility deeper within the liver and impeded imaging of the diaphragm Figure 6 Hepatic steatosis(fatty liver). Sonographic signs of hepatic steatosis include hepatomegaly with rounded borders, increased echogenicity, ultrasound attenuation caused by absorption, scattering, and beam divergence and decreased detail display of intra-hepatic vascular architecture. There is exageration of the difference between the kidney parenchyma and liver echogenicity. Right kidney is shown between callipers(+) In the majority of patients with hepatic steatosis, distinctive hypoechoic areas in the liver hilum can be demonstrated by ultrasound examination [Figure 7][7; 28 38)].It
Liver pathology - diffuse liver disease Criteria for analysing diffuse liver disease include evaluation of - liver parenchyma (echo texture, ultrasound attenuation, vascular architecture, etc.) as well as its surface (a high frequency transducer is helpful in detecting more details of the superficially located structures); - liver hilum structures including perihepatic lymph nodes in the hepatoduodenal ligament, lymph nodes in inflammatory liver disease or neoplastic infiltration; - analysis of hepatic vessel flow patterns using colour and pulsed wave Doppler imaging (CDI). Ultrasound contrast agents (USCA) have improved the detection/exclusion rate of focal liver lesions; in diffuse liver disease, USCA potential is much lower (e.g., hepatic transit time). Hepatic steatosis Hepatic steatosis is the most common liver pathology. Sensitivity and specificity of the detection of hepatic steatosis by B-mode ultrasound examination may be very high in the hands of an expert investigator who consistently applies specific criteria in patients with significant fatty liver disease. In transabdominal ultrasound, hepatic steatosis is characterised by increased echogenicity, which is often compared to the spleen or kidney parenchyma at the same depth [Figure 6]. Supporting findings may be ultrasound attenuation, which means a decrease in intensity as sound travels through a material, caused by absorption, scattering, and beam divergence. Attenuation decreases detail analysis of vascular architecture, and it may cause a loss of visibility deeper within the liver and impeded imaging of the diaphragm. Figure 6 Hepatic steatosis (fatty liver). Sonographic signs of hepatic steatosis include hepatomegaly with rounded borders, increased echogenicity, ultrasound attenuation caused by absorption, scattering, and beam divergence and decreased detail display of intra-hepatic vascular architecture. There is exageration of the difference between the kidney parenchyma and liver echogenicity. Right kidney is shown between callipers (+). In the majority of patients with hepatic steatosis, distinctive hypoechoic areas in the liver hilum can be demonstrated by ultrasound examination [Figure 7] [(7;28;38)]. It
is believed that the presence of focal hypoechoeic areas(FHa) within the liver hilum (and elsewhere in the liver )corresponds to parenchymal islands with(close to) normal fat content (due to a locally different blood supply), that are surrounded and contrasted by bright echogenic parenchyma with fatty infiltration. Subcapsular FhA and FHa close to liver veins are other typical locations, the shape of these pseudolesions" being polycyclic and non-round. FHA are relatively specific for hepatic steatosis and may be helpful to differentiate fatty from fibrotic liver disease Similar focal hypoechoeic areas were demonstrated in patients with liver steatosis due to systemic corticosteroid therapy, even though the more important focal lesions in this condition are hyperechoic [Figure 8]. Pathophysiologically areas of different fat content might be explained by a different arterial and portal venous blood supply in comparison to the surrounding liver parenchyma which is mainly portal venous and contains, therefore, a higher fat and insulin concentration in focal fatty infiltration [(32;38) Figure 7 Hepatic steatosis. Perhaps the most objective and therefore most important sign of hepatic steatosis are circumscribed focal hypoechoic areas in the liver hilum examined in a left posterior oblique position. B-mode ultrasound demonstrates a focal liver lesion in between calipers(a). Colour Doppler imaging indicates a centrally located vessel of undetermined origin(b) a Figure 8 Hepatic steatosis indicated by focal hyperechoic ([(28)) areas in the liver hilum They are characterised by centrally located(portal) vein branches identified by colour Doppler imaging(a), spectral analysis and CEUS (b). Such lesions also typically found subcapsular next to the teres ligament [(28)1 Distanz=3.20cm
is believed that the presence of focal hypoechoeic areas (FHA) within the liver hilum (and elsewhere in the liver) corresponds to parenchymal islands with (close to) normal fat content (due to a locally different blood supply), that are surrounded and contrasted by bright echogenic parenchyma with fatty infiltration. Subcapsular FHA and FHA close to liver veins are other typical locations, the shape of these “pseudolesions” being polycyclic and non-round. FHA are relatively specific for hepatic steatosis and may be helpful to differentiate fatty from fibrotic liver disease. Similar focal hypoechoeic areas were demonstrated in patients with liver steatosis due to systemic corticosteroid therapy, even though the more important focal lesions in this condition are hyperechoic [Figure 8]. Pathophysiologically areas of different fat content might be explained by a different arterial and portal venous blood supply in comparison to the surrounding liver parenchyma which is mainly portal venous and contains, therefore, a higher fat and insulin concentration in focal fatty infiltration [(32;38)]. Figure 7 Hepatic steatosis. Perhaps the most objective and therefore most important sign of hepatic steatosis are circumscribed focal hypoechoic areas in the liver hilum examined in a left posterior oblique position. B-mode ultrasound demonstrates a focal liver lesion in between calipers (a). Colour Doppler imaging indicates a centrally located vessel of undetermined origin (b). a b Figure 8 Hepatic steatosis indicated by focal hyperechoic ([(28)] areas in the liver hilum. They are characterised by centrally located (portal) vein branches identified by colour Doppler imaging (a), spectral analysis and CEUS (b). Such lesions are also typically found subcapsular next to the teres ligament [(28)]. a b
Iver cirrhosis The accuracy of ultrasound in the correct diagnosis of "liver cirrhosis"in patients with complications(ascites, splenomegaly, collaterals)is high(> 90 %) In the initial stages and in micronodular cirrhosis, it may be overlooked in up to 30 %[(32)1 Sonographic signs of liver cirrhosis include inhomogenous echotexture and irregular-nodular liver surface delineation and a variety of other possible findings including destroyed vascular architecture also dependent on the etiology of diseases IFigure 9]. Dysproportional segment atrophy (and also hypertrophy has been observed [Figure 10] Figure 9 Liver cirrhosis. Typical signs of liver cirrhosis include inhomogenous echotexture and irregular liver surface delineation(a, arrow). In addition distinctive nodules are suggestive(b). Sometimes it might be difficult to identify the liver parenchyma, therefore the organ is indicated as well: Leber: liver Nodular liver surface(especially using high frequency transducers) has an excellent positive predictive value close to 100 for cirrhosis. A disproportional volume enlargement of the caudate lobe in relation to the right and left lobe may be indicative of liver cirrhosis but this sign is of limited value in daily clinical practice Coarse liver parenchyma and a disturbed or destroyed vascular architecture as a sig of portal hypertension- such as reversed portal flow and collateral vessels- are other signs of liver cirrhosis. In Doppler studies, a raise in the arterioportal peak velocity ratio(maximum velocity of the hepatic artery divided through the maximum velocity of the vena portae)of more than 3.5 is predictive for cirrhosis. The positive predictive value of the detection of signs of portal hypertension is excellent such as reversed portal flow and the detection of collateral vessels. The negative predictive value is worse. Overall, the accuracy is about 60 % An enlarged portal vein diameter greater than 1.25 cm or a reduced portal vein flow velocity indicates cirrhosis with a sensitivity and specificity of about 80 % All mentioned parameters, however, are of limited val Figure 10 Liver lobes and segments may behave different during the course of a disease, as shown in this patient with systemic scleroderm with gradually shrinkage of the right liver lobe(in between markers). The changes of the liver evolved gradually over the last ten years
Liver cirrhosis The accuracy of ultrasound in the correct diagnosis of “liver cirrhosis” in patients with complications (ascites, splenomegaly, collaterals) is high (> 90 %). In the initial stages and in micronodular cirrhosis, it may be overlooked in up to 30 % [(32)]. Sonographic signs of liver cirrhosis include inhomogenous echotexture and irregular-nodular liver surface delineation and a variety of other possible findings including destroyed vascular architecture also dependent on the etiology of diseases [Figure 9]. Dysproportional segment atrophy (and also hypertrophy) has been observed [Figure 10]. Figure 9 Liver cirrhosis. Typical signs of liver cirrhosis include inhomogenous echotexture and irregular liversurface delineation (a, arrow). In addition distinctive nodules are suggestive (b). Sometimes it might be difficult to identify the liver parenchyma, therefore the organ is indicated as well: Leber: liver. a b Nodular liver surface (especially using high frequency transducers) has an excellent positive predictive value close to 100 % for cirrhosis. A disproportional volume enlargement of the caudate lobe in relation to the right and left lobe may be indicative of liver cirrhosis but this sign is of limited value in daily clinical practice. Coarse liver parenchyma and a disturbed or destroyed vascular architecture as a sign of portal hypertension - such as reversed portal flow and collateral vessels - are other signs of liver cirrhosis. In Doppler studies, a raise in the arterioportal peak velocity ratio (maximum velocity of the hepatic artery divided through the maximum velocity of the vena portae) of more than 3.5 is predictive for cirrhosis. The positive predictive value of the detection of signs of portal hypertension is excellent such as reversed portal flow and the detection of collateral vessels. The negative predictive value is worse. Overall, the accuracy is about 60 %. An enlarged portal vein diameter greater than 1.25 cm or a reduced portal vein flow velocity indicates cirrhosis with a sensitivity and specificity of about 80 %. All mentioned parameters, however, are of limited value. Figure 10 Liver lobes and segments may behave different during the course of a disease, as shown in this patient with systemic sclerodermy with gradually shrinkeage of the right liver lobe (in between markers). The changes of the liver evolved gradually over the last ten years