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Hagen Chapter 9 Liver

Terms in this set (50)

Segments of the liver
Segment I: Caudate lobe
Segments II and III: Left superior and inferior lateral segments
Segments IVa and IVb: Medial segments of the left lobe
Segments V and VI: Caudal to the transverse plane
Segments VII and VIII: Cephalad to the transverse plane
Ligaments and Fissures
Appear echogenic or hyperechoic because of the presence of collagen and fat within and around the structures:
Glisson capsule
Main lobar fissure
Falciform ligament
Ligamentum teres (round ligament)
Ligamentum venosum
Vascular supply
Portal Venous System
Main portal vein
Right portal vein
Left portal vein
Hepatic Venous System
Portal veins carry blood from the bowel to the liver, whereas the hepatic veins drain the blood from the liver into the inferior vena cava.
Hepatic arteries carry oxygenated blood from the aorta to the liver.
Bile ducts transport bile, which is manufactured in the liver, to the duodenum.
anatomy of liver
Occupies the right hypochondrium, the greater part of the epigastrium, and the left hypochondrium as far as the mammillary line
Contour and shape vary
Lies inferior to the diaphragm
Ribs cover the greater part of the right lobe
In the epigastric region, the liver extends several centimeters below the xiphoid process
Primary function of liver
Hepatic metabolic functions
The major site for converting dietary sugars (carbohydrates) into glucose
Converts glucose to glycogen and stores it; when glucose is needed, it breaks down the glycogen and releases glucose into the blood
Major site for metabolizing fats
Dietary fats are converted in the hepatocytes to lipoproteins, the form in which fats are transported throughout the body for storage or use.
Stored fats may be transported to the liver and converted into energy.
liver funtions
Manufactures plasma proteins
Converts excess amino acids to fatty acids and urea
Removes nutrients from the blood
Phagocytizes bacteria and worn-out red blood cells
Secretes bile, which is important in the digestion of fats
Bilirubin, a pigment released when red blood cells are broken down, is excreted in the bile
Stores iron and certain vitamins
Detoxifies many drugs and poisons that enter the body, as well as waste products of the body's metabolic processes.
Hepatic versus Obstructive Disease
Hepatocellular disease
Liver cells (hepatocytes) are the immediate problem.
Usually treated medically with supportive measures and drugs
Obstructive disorders
Bile excretion is blocked.
Usually treated surgically
Bilirubin Detoxification
Bilirubin, the breakdown product of hemoglobin, is also an important substance detoxified in the liver.
Liver excretes bilirubin into the gut via the biliary tree.
Red blood cells survive an average of 120 days in the circulatory system; they are then trapped and broken down by reticuloendothelial cells, primarily in the spleen.
Hemoglobin released from the red cells is converted to bilirubin within the reticuloendothelial system and is then released into the bloodstream.
Bilirubin molecules become attached to albumin in the blood and are transported to the liver.
Metabolism of bilirubin in the hepatocytes
Uptake: Bilirubin is separated from albumin, probably at the cell membrane, and is taken inside the hepatocytes.
Conjugation: Bilirubin molecule is combined with two glucuronide molecules, forming bilirubin diglucuronide.
Excretion: Bilirubin molecule is actively transported across the cell membrane into the bile canaliculi, which are the microscopic "headwaters" of the biliary system. Bilirubin released from the hepatocytes passes through the bile ducts with other components of bile and is delivered to the bowel.
Bile
Excretory product of the liver
Formed continuously by the hepatocytes, collects in the bile canaliculi adjacent to these cells, and is transported to the gut via the bile ducts.
Principal components: water, bile salts, and bile pigments (primarily bilirubin diglucuronide)
Other components: cholesterol, lecithin, and protein
Primary functions of bile
Emulsification of intestinal fat
Removal of waste products excreted by the liver
LFT
Aspartate aminotransferase (AST)
Alanine aminotransferase (ALT)
Lactic acid dehydrogenase (LDH)
Alkaline phosphatase (alk phos)
Bilirubin (indirect, direct, total)
Prothrombin time (PT)
Albumin and globulins
Sonographic Evaluation of the Liver
Patient preparation
Nothing by mouth (NPO) for 6 hours to eliminate bowel gas and ensure fullness of gallbladder
Patient position
Supine or right anterior oblique position, usually with deep inspiration to allow the liver to move inferior to the rib cage
Complete survey: transverse, coronal, subcostal oblique, and sagittal views.
Thin-walled hepatic veins, brightly reflective portal veins, hepatic arteries, and the hepatic duct lie within the homogeneous parenchyma.
With color-flow Doppler imaging, the hepatic portal flow is shown to be hepatopetal (toward the liver), and the hepatic venous flow is hepatofugal (away from the liver).
Assessment criteria
Size of the liver in the longitudinal plane
Attenuation of the liver parenchyma
Liver texture
Presence of hepatic vascular structures, ligaments, and fissures
Normal Texture
Homogeneous with fine-low level echoes
Minimally hyperechoic to isoechoic, when compared with the renal cortex of the kidneys
Hypoechoic, when compared with the texture of the spleen
technique
Adequate technique demands that each patient be examined with the following criteria:
Size of the liver in the sagittal plane ~15 cm
Parenchyma ~ homogeneous
Liver texture > right kidney; <pancreas, <spleen
Presence of hepatic vascular structures, ligaments, fissures
Surface ~ smooth
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