Liver Cross Sectional Anatomy

LIVER NORMAL ANATOMY  Intraperitoneal Size males 1600 grams females 1200 grams tranverse 20-22.5 cm anterior to posterior 10-12.5 cm length (rt lobe) 15-17 cm  LIVER COVERINGS Glisson’s Capsule broelastic connective tissue contain’s blo...

LIVER NORMAL ANATOMY  Intraperitoneal Size males 1600 grams females 1200 grams tranverse 20-22.5 cm anterior to posterior 10-12.5 cm length (rt lobe) 15-17 cm  LIVER COVERINGS Glisson’s Capsule broelastic connective tissue contain’s blood, lymphatics, and nerves Peritoneum loose, mesh-like covering covers almost entire liver surface except for attachement of falciform ligament, porta hepatis, IVC, GB fossa, and “bare area” fi  Right Lobe largest separated from left lobe by main lobar fissure anterior/posterior division by right hepatic vein Left lobe anterior to pancreas medial/lateral division by left portal vein Caudate lobe smallest located posterior to left lobe separated from left lobe by ligamentum venosum Quadrate Lobe medial aspect of left lobe anterior to porta hepatis between GB fossa and ligamentum Teres  LOBAR DIVISION Traditional Lobar Anatomy Divides liver into four lobes right, left, caudate, and quadrate based on external landmarks Functional Lobar Anatomy Divides liver into three lobes right, left, and caudate based on vascular supply and drainage Couinaud’s Anatomy Divides liver into eight sections method for hepatic lesion localization each section has own portal vein, hepatic artery and bile duct  LIGAMENTS AND FISSURES Main lobar fissure divides liver into right and left joins GB fossa and RPV Falciform ligament separates right from left lobe on diaphragmatic surface gives rise to ligamentum teres Ligamentum teres (round) continuation of falciform ligament remnant of umbilical vein Ligamentum venosum separates left lobe from caudate lobe results from ductous venosus after birth 11 10  NORMAL VARIANTS Reidel’s Lobe “tongue-like” projection extending inferiorly past lower pole of right kidney ^ females Situs Inversus Pseudo ssures indentions of diaphragm Papillary process inferior extension of caudate lobe fi  VASCULAR SUPPLY Hepatic veins carry blood from liver to IVC Portal veins carry blood from intestines to liver 70-80% of blood supply to the liver Hepatic artery supplies blood from aorta to liver 20-30% of blood supply to the liver  HEPATIC VEINS empty blood from liver into IVC just superior to renal veins increase in diameter closer to IVC intersegmental and interlobar normal diameter = 4-7 mm hepatofugal flow (away from liver) Doppler waveforms exhibit triphasic waveform due atrial contraction walls are less echogenic when compared to portal veins  HEPATIC VEINS CONT’D 3 major veins: right drains right lobe divides right lobe of liver into anterior and posterior portions middle drains caudate lobe divides liver into right and left portions left drains left lobe divides left lobe of liver into medial and lateral segments  Figure 2. Diagram shows a normal venous spectrum obtained with Doppler US, which includes a, S, v, and D waves that represent back-pulsations caused by right atrial pressure changes during the cardiac cycle. Chavhan G B et al. Radiographics 2008;28:691-706 ©2008 by Radiological Society of North America  PORTAL VEINS Main portal vein originates just to right of midline at junction of splenic vein and superior mesenteric vein. bifurcates into right and left portal veins at porta hepatis diameter < 13mm Right portal vein larger than left portal vein runs centrally and horizontally in right lobe anterior and posterior branches branches divide right lobe into anterior and posterior segments Left portal vein smaller than right portal vein divides left lobe into medial and lateral aspects 26 18 28  DISTINGUISHING CHARACTERISTICS OF HEPATIC AND PORTAL VEINS PORTAL VEINS HEPATIC VEINS Blood ow out/away from liver Blood ow into liver (hepatofugal) (hepatopetal) walls are less echogenic portal veins Portal vein walls are more echogenic than hepatic vein walls. “Portals wear pajamas !” fl fl  HEPATIC ARTERY Branches off of celiac axis Low resistance arterial waveform supplies 20-30 % of blood to liver Bifurcates into gastroduodenal artery, supraduodenal artery and right gastric artery and hepatic artery proper  ULTRASOUND APPEARANCE Smooth, homogeneous echotexture Slightly hyperechoic or isoechoic to kidney Isoechoic to spleen PHYSIOLOGY  METABOLISM Carbohydrates converts necessary dietary sugar into glucose and stores excess sugar in the form of glycogen in times of de cient dietary sugar, converts stored glycogen into glucose Fats hepatocytes convert dietary fat into lipoproteins which are stored or used by other organs Proteins produces albumin which helps regulate osmotic pressure produces blood coagulation proteins such as brinogen and prothrombin fi fi  DIGESTION Nutrients from food are absorbed in the walls of the small intestine and enter the portal venous system Bile manufactured in the liver emulsi es fat in the intestines and removes waste products excreted by the liver fi  DETOXIFICATION Ammonium is converted to nontoxic urea and excreted by the kidneys Bilirubin a by-product of red blood cell breakdown, is removed from blood stream and stored in hepatocytes where it is converted to bile and is then released through the bile ducts breakdown of hormones, medications, and foreign chemicals  STORAGE Glycogen Amino acids Fats Vitamins A, D, and B, complex Iron and Copper Blood reservoir PERTINENT LAB VALUES  AST and ALT ^ in cases of severe hepatocellular disease. very high levels LACTIC ACID DEHYDROGENASE mildly elevated with hepatitis, cirrhosis, and obstructive jaundice ALKALINE PHOSPHATASE sensitive indicator of biliary obstruction  Prothrombin time clotting factor produced with adequate intake of vitamin K increased clotting times seen in cases of cirrhosis and metastatic disease Albumin decreases with suppression of protein synthesis seen decreased with chronic liver disease such as cirrhosis Alpha feto-protein (AFP) increased with liver malignancies  Bilirubin-product of hemoglobin breakdown in red blood cells. Excess bilirubin is leaked into tissues and skin and sclera becomes jaundiced (yellow) Indirect (unconjucated)- caused from increased destruction of red blood cells with anemia, or hemorrhage Direct (conjucated)- caused by obstruction from stones, masses, or hepatocellular disease