EFSUMB-European Course Book Editor: Christoph F. Dietrich Ultrasound of the liver Christoph F. Dietrich, Carla Serra, Maciej Jedrzejczyk University of Bologna. Department of Diagnostic Imaging, 2nd Medical Faculty of arsaw Medical University Acknowledgment: The authors thank Lucas Greiner, Julie Walton, loan Sporea, Christian Nolsoe and Norbert Gritzmann for peer review of the manuscript
EFSUMB – European Course Book Editor: Christoph F. Dietrich Ultrasound of the liver Christoph F. Dietrich, Carla Serra 2 , Maciej Jedrzejczyk 3 2 University of Bologna. 3 Department of Diagnostic Imaging, 2nd Medical Faculty of Warsaw Medical University. Acknowledgment: The authors thank Lucas Greiner, Julie Walton, Ioan Sporea, Christian Nolsoe and Norbert Gritzmann for peer review of the manuscript
Content Content Topographic Remarks Liver anatomy Ultrasound Examination technique Patient Preparation Examination Liver pathology -diffuse liver disease 8 Hepatic steatosis Liver cirrhosis Chronic viral hepatitis C Primary biliary cirrhosis(PBC) Doppler ultrasound techniques in the evaluation of liver disease Anatomy, blood supply of hepatic vessels Arterial flow 12 Portal venous system Venous outflow Vascular(Doppler) indices 13 Examination of the portal vein in patients with diffuse liver disease 13 Normal and pathological portal venous blood flow Portal hypertension No portal venous blood flow 14 Retrograde portal venous blood flow 14 Portal vein thrombosis Examination of the hepatic veins in patients with diffuse liver disease Hepatic venous outflow obstruction(Budd Chiari-syndrome, BCS) Liver pathology -detection and characterisation of focal liver lesions(FLL) Liver tumour detection .17 Differentiation of benign and malignant lesions Focal liver lesion(liver tumour)characterisation 19 L Haemangioma Hepatocellular carcinoma(HCC) Metastase Abscess Clinical importance of liver ultrasound in daily routine References
Content Content........................................................................................................................1 Topographic Remarks......................................................... ........................................2 Liver anatomy..............................................................................................................3 Ultrasound Examination technique..............................................................................4 Patient Preparation...................................................................................................4 Examination.............................................................................................................4 Liver pathology - diffuse liver disease...................................................................... ..8 Hepatic steatosis......................................................................................................8 Liver cirrhosis......................................................................................................... 9 Chronic viral hepatitis C......................................................................................... 10 Primary biliary cirrhosis (PBC)...............................................................................10 Doppler ultrasound techniques in the evaluation of liver disease................................11 Anatomy, blood supply of hepatic vessels............................................................ . 11 Arterial flow........................................................................................................12 Portal venous system...........................................................................................12 Venous outflow............................................................................................ ..... .13 Vascular (Doppler) indices.......................................................................... .. ... 13 Examination of the portal vein in patients with diffuse liver disease.............. . ..13 Normal and pathological portal venous blood flow................................... ... ... 13 Portal hypertension..............................................................................................14 No portal venous blood flow................................................................................14 Retrograde portal venous blood flow...................................................................14 Portal vein thrombosis..........................................................................................15 Examination of the hepatic veins in patients with diffuse liver disease...................16 Hepatic venous outflow obstruction (Budd Chiari-syndrome, BCS).............. ....16 Liver pathology - detection and characterisation of focal liver lesions (FLL).............16 Liver tumour detection.................................................................................... ........17 Differentiation of benign and malignant lesions......................................... ............18 Focal liver lesion (liver tumour) characterisation....................................................19 Liver cyst..............................................................................................................18 Haemangioma.......................................................................................................19 Hepatocellular carcinoma (HCC)........................................................................ 20 Metastases............................................................................................................21 Abscess.................................................................................................................21 Clinical importance of liver ultrasound in daily routine........................................... ..24 References....................................................................................................................25
Topographic Remarks The liver is located intraperitonealy, and under the right hemi-diaphragm but also extend across the midline reach to the left hemi-diaphragm and to the spleen in some cases. The liver is fixed to the diaphragm by the pars affixa and to the ventral abdominal wall by the ligamentum falciforme(falciform ligament)and its strong margin, the ligamentum teres hepatis. The minor omentum consists of the ligamentum hepatogastricum and of the ligamentum hepatoduodenale. The hepatoduodenal ligament carries three vessels-two containing blood(the portal vein and hepatic artery), and one carrying bile(common bile duct). The further courses of these three vessels is mainly parallel( Glisson's triad) The structures of the liver hilum(porta hepatis)are panied by a number of (in relation to the portal vein) ventrally and dorsally lymph nodes which can routinely be demonstrated by ultrasound (US). The liver has three main veins(hepatic veins)- left, middle and right one which drain the liver blood to the retroperitoneally located inferior vena cava. The inferior vena cava is variably surrounded by liver parenchyma The organs and structures surrounding the liver are the organs of the peritoneal cavity and but also pleural and pericardial structures. Neighbourhood structures adjacent to the liver are numerous, including(clockwise) basal lung proportions separated by the muscular layers of the right diaphragm(and more or less extensively also of the left diaphragm too), heart, stomach, intestine(e.g, upper duodenal loop and right colonic flexure), abdominal aorta, inferior vena cava, right adrenal gland and right kidney Interposition of the colon between liver and the anterior abdominal wall can prevent the sonographic approach to the right liver lobe in case of Chilaiditi's syndrome. In the case of complete or incomplete situs inversus the topographic relations are inverted Liver anatomy Anatomic orientation Liver anatomy is defined by ligaments and fissures as well as by the vascular architecture: branches of the hepatic artery, portal vein, and bile ducts in their parallel course define the centers of liver segment anatomy Liver segment anatom A simplified anatomy divides into the larger right lobe(including segment V, VI, VIl VIID), the left lobe with its medial(IVa, b) and lateral segments(Il, III), and the caudate lobe D) Couinaud classification Liver segment anatomy is explained by the widely accepted architecture described by Couinaud [(16, 17)]. The Couinaud classification, modified by Bismuth(segment IVa b), is based on 8 segments, each of which has its own arterial and portal venous vessel
Topographic Remarks The liver is located intraperitonealy, and under the right hemi-diaphragm but also extend across the midline reach to the left hemi-diaphragm and to the spleen in some cases. The liver is fixed to the diaphragm by the pars affixa and to the ventral abdominal wall by the ligamentum falciforme (falciform ligament) and its strong margin, the ligamentum teres hepatis. The minor omentum consists of the ligamentum hepatogastricum and of the ligamentum hepatoduodenale. The hepatoduodenal ligament carries three vessels – two containing blood (the portal vein and hepatic artery), and one carrying bile (common bile duct). The further courses of these three vessels is mainly parallel (Glisson`s triad). The structures of the liver hilum (porta hepatis) are accompanied by a number of (in relation to the portal vein) ventrally and dorsally located lymph nodes which can routinely be demonstrated by ultrasound (US). The liver has three main veins (hepatic veins) – left, middle and right one – which drain the liver blood to the retroperitoneally located inferior vena cava. The inferior vena cava is variably surrounded by liver parenchyma. The organs and structures surrounding the liver are the organs of the peritoneal cavity and but also pleural and pericardial structures. Neighbourhood structures adjacent to the liver are numerous, including (clockwise) basal lung proportions separated by the muscular layers of the right diaphragm (and more or less extensively also of the left diaphragm too), heart, stomach, intestine (e.g., upper duodenal loop and right colonic flexure), abdominal aorta, inferior vena cava, right adrenal gland and right kidney. Interposition of the colon between liver and the anterior abdominal wall can prevent the sonographic approach to the right liver lobe in case of Chilaiditi’s syndrome. In the case of complete or incomplete situs inversus the topographic relations are inverted. Liver anatomy Anatomic orientation Liver anatomy is defined by ligaments and fissures as well as by the vascular architecture: branches of the hepatic artery, portal vein, and bile ducts in their parallel course define the centers of liver segment anatomy. Liver segment anatomy A simplified anatomy divides into the larger right lobe (including segment V, VI, VII, VIII), the left lobe with its medial (IVa,b) and lateral segments (II, III), and the caudate lobe (I). Couinaud classification Liver segment anatomy is explained by the widely accepted architecture described by Couinaud [(16;17)]. The Couinaud classification, modified by Bismuth (segment IVa, b), is based on 8 segments, each of which has its own arterial and portal venous vessel
architecture( Glisson's triad) indicating vascular inflow, outflow, and biliary drainag [9; 10)1. Because of this division into self-contained units, each can be resected (alone or in groups) without damaging those remaining as the vascular inflow, outflow and biliary drainage is preserved. Depending on the 3D volume orientation of the liver (longitudinal or oblique orientated) interpretation of Couinaud classification unfortunately finds some inconsistency in literature. While the portal vein plane has often been described as transverse, it may be oblique since the left branch runs superiorly and the right branch runs inferiorly. In addition to forming an oblique transverse plane between segments, the left and right portal veins branch superiorly and inferiorly to project into the centre of each segment Ultrasound Examination technique Patient Preparation It is recommended that a patient undergo a period of fasting prior to upper abdominal imaging to maximise the distension of the gall bladder and to reduce food residue and gas in the upper GI tract which may reduce image quality or precluded liver imaging This is essential for full imaging of the liver and related biliary tree but may not be required in an acute situation such as trauma where imaging of the gall bladder is not immediately essential. a patient may take small amounts of still water by mouth prior to scan, particularly for taking any medications. There is some evidence that smoking can reduce image quality when scanning upper abdominal structures and it is good practice to encourage a patient not to smoke for 6-8 hours prior to US scan. Smoking increases gas intake into upper GI tract and may reduce image quality. Also, some chemicals in tobacco are known to cause contraction of the smooth muscle of the gi tract and this can cause contraction of the gall bladder, even when fasting has occurred, and the gall bladder cannot be scanned E The liver is a large, pyramidal shaped organ and liver sectional anatomy may be best described imaged and defined using by real time ultrasound imaging. Conventional eal time ultrasound produces images of thin slices of the liver on the screen, and so it is essential that the operator scans the entire organ systematically/ritually, in at least two anatomical planes, to be entirely convinced that the entire volume of the liver tissue and structures has been imaged. The operator must then synthesise this 2 dimensional information in their brain to develop a 3 dimensional map of the individual patients liver anatomy and pathology. This requires good hand-eye-brain coordination For orientation, three levels of the central portion of the liver can be differentiated Level of the Confluences of the liver veins [Figure 1] Level of the Pars umbilicalis of the(left) portal vein branch [Figure 2] Level of the gall bladder Figure 3 Figure 1 Confluences of the liver veins. This "junction" level is the first one in ultrasound examination of the right liver lobe by subcostal scanning sections steeply looking"upwards, preferably in deep inspiration [video]. VCI: inferior vena cava. LLV: Left liver vein. MLV. Middle liver vein. C: Confluens of the llv and MLV RLV: Right liver vein. The rlv often separately joins the inferior
architecture (Glisson`s triad) indicating vascular inflow, outflow, and biliary drainage [(9;10)]. Because of this division into self-contained units, each can be resected (alone or in groups) without damaging those remaining as the vascular inflow, outflow and biliary drainage is preserved. Depending on the 3D volume orientation of the liver (longitudinal or oblique orientated) interpretation of Couinaud classification unfortunately finds some inconsistency in literature. While the portal vein plane has often been described as transverse, it may be oblique since the left branch runs superiorly and the right branch runs inferiorly. In addition to forming an oblique transverse plane between segments, the left and right portal veins branch superiorly and inferiorly to project into the centre of each segment. Ultrasound Examination technique Patient Preparation It is recommended that a patient undergo a period of fasting prior to upper abdominal imaging to maximise the distension of the gall bladder and to reduce food residue and gas in the upper GI tract which may reduce image quality or precluded liver imaging. This is essential for full imaging of the liver and related biliary tree but may not be required in an acute situation such as trauma where imaging of the gall bladder is not immediately essential. A patient may take small amounts of still water by mouth prior to scan, particularly for taking any medications. There is some evidence that smoking can reduce image quality when scanning upper abdominal structures and it is good practice to encourage a patient not to smoke for 6-8 hours prior to US scan. Smoking increases gas intake into upper GI tract and may reduce image quality. Also, some chemicals in tobacco are known to cause contraction of the smooth muscle of the GI tract and this can cause contraction of the gall bladder, even when fasting has occurred, and the gall bladder cannot be scanned. Examination The liver is a large, pyramidal shaped organ and liver sectional anatomy may be best described imaged and defined using by real time ultrasound imaging. Conventional real time ultrasound produces images of thin slices of the liver on the screen, and so it is essential that the operator scans the entire organ systematically/ritually, in at least two anatomical planes, to be entirely convinced that the entire volume of the liver tissue and structures has been imaged. The operator must then synthesise this 2 dimensional information in their brain to develop a 3 dimensional map of the individual patient`s liver anatomy and pathology. This requires good hand-eye-brain coordination. For orientation, three levels of the central portion of the liver can be differentiated: • Level of the Confluences of the liver veins [Figure 1]. • Level of the Pars umbilicalis of the (left) portal vein branch [Figure 2]. • Level of the gall bladder [Figure 3]. Figure 1 Confluences of the liver veins. This “junction” level is the first one in ultrasound examination of the right liver lobe by subcostal scanning sections steeply “looking” upwards, preferably in deep inspiration [video]. VCI: inferior vena cava. LLV: Left liver vein. MLV: Middle liver vein. C: Confluens of the LLV and MLV. RLV: Right liver vein. The RLV often separately joins the inferior
vena cava, whereas the llv and Mlv often reveal a common trunk(C Figure 2"Pars umbilicalis"of the portal vein- scanning planes display the left and right liver lobes in a more downwards orientated view into the right liver lobe as compared to the level of the confluens of the liver veins. PA: Portal vein. PU pars umbilicalis of the portal vein VCI: Inferior vena cava Figure 3 Gallbladder level as the most caudate scanning plane. GB: Gallbladder. LTH LIgamentum teres hepatis. s4 Segment IV of the liver(quadrate lobe) e:24+a Analysing the ultrasound examination, these levels mean the access for a number of (more or less)parallel scanning sections, which in there summary in the examiner brain form an real time three dimensional (4D)copy of the given patients individual anatomy and pathology Standardised scanning in a ritualized sequence of probe- and patient positions and of
vena cava, whereas the LLV and MLV often reveal a common trunk (“C”). Figure 2 “Pars umbilicalis” of the portal vein – scanning planes display the left and right liver lobes in a more downwards orientated view into the right liver lobe as compared to the level of the confluens of the liver veins. PA: Portal vein. PU: pars umbilicalis of the portal vein. VCI: Inferior vena cava. Figure 3 Gallbladder level as the most caudate scanning plane. GB: Gallbladder. LTH: LLigamentum teres hepatis. S4: Segment IV of the liver (quadrate lobe). Analysing the ultrasound examination, these levels mean the access for a number of (more or less) parallel scanning sections, which in there summary in the examiner`s brain form an real time three dimensional (“4D”) copy of the given patient`s individual anatomy and pathology. Standardised scanning in a ritualized sequence of probe- and patient positions and of
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