Liver Anatomy, Physiology, and Ultrasound Appearance

Section 3.1: Liver Introduction

• Largest peritoneal organ with numerous bodily functions.
• Major focus for diagnosing diseases via ultrasound.
• Importance for sonographers to understand liver anatomy and physiology.
  • Includes global and detailed anatomical studies.
  • Covers microanatomy and macroanatomy.
• Ultrasound focuses on structure identification, landmarks, and protocols.

Section 3.2: Global Anatomy of the Liver

• "Global anatomy" encompasses relational anatomy of the liver.
• Importance of relational anatomy: helps to visualize and locate organs via ligaments and surrounding structures.
• Understanding embryology is beneficial:
  • Liver forms at 4 weeks of gestation, engages in hematopoiesis by week 5.
• Nine-region system locates liver mostly in right hypochondrium, can extend to epigastric and left hypochondriac regions.
• Major landmarks around the liver:
  • Diaphragm (superior), thoracic spine (posterior), right costal margin (lateral and anterior), rectus abdominis (anterior).
• Organs surrounding the liver:
  • Diaphragm, gallbladder, right kidney, pancreas, stomach, duodenum.
• Two coverings:
  • Glisson’s capsule (fibrous, covers liver completely).
  • Peritoneum (partially covers liver, except bare area).
• Liver ligaments:
  • Eight ligaments: Coronary, Right/Left Triangular, Falciform, Ligamentum Teres, Ligamentum Venosum, Gastrohepatic, Hepatoduodenal.
  • Ligaments help anchor the liver and provide structural support.

Section 3.3: Lobe Division

• Liver divided into four anatomical lobes via ligaments: Right, Left, Quadrate, Caudate.
• Anterior division by Falciform ligament.
• Posterior division by IVC, caudate lobe, porta hepatis, gallbladder fossa.

Section 3.4: Liver Vasculature

• Liver is supplied by the hepatic artery and portal vein.
• Porta Hepatis: entry/exit point for liver vessels.
• Portal Triad: Portal vein, Hepatic artery, Bile duct.
• Hepatic Artery Pathway: Aorta → Celiac axis → Common hepatic artery → Proper hepatic artery → R/L hepatic arteries.
• Portal Vein Pathway: Inferior mesenteric vein + Splenic vein → Portal confluence → Main portal vein → R/L portal veins.
• Hepatic Veins (Right, Middle, Left) drain into IVC.

Section 3.5: Segmental Division

• Internal landmarks (vessels/bile ducts) divide liver into functional segments.
• Anatomic division: 4 lobes; Segmental division: 3 lobes.
• Segmental Division:
  • Caudate lobe: remains independent.
  • Left lobe: Left lateral and medial segments.
  • Right lobe: Right anterior and posterior segments.
• Segments are further divided into Quinaud’s anatomy (8 segments).

Section 3.6: Anatomical Variants of the Liver

• Variants include situs inversus, left lobe agenesis, beaver tail, Riedel’s lobe.
• Hepatic vein variants: common, can affect ultrasound imaging.

Section 3.7: Liver Microanatomy

• Liver composed of lobules with functional units.
• Lobule Structure: Central vein, portal triad parts, hepatocytes (regeneration and function).
• Sinusoids: Capillaries between hepatocytes, contain Kupffer cells for detoxification.

Section 3.8: Liver Physiology

• Complex functions: metabolism, protein synthesis, storage, detoxification, bile production, blood reservoir, lymph production.
• Metabolism: Carbohydrates (glycogen storage), proteins (amino acid breakdown with AST/ALT), fats (cholesterol management).
• Protein Synthesis: Albumin (fluid balance), blood clotting factors (e.g., prothrombin).
• Storage: Glycogen, vitamins (A, D, E, K, B12), minerals.
• Detoxification: Xenobiotics, bilirubin (conjugation process).
• Bile Production: Bile ductules transport to gallbladder.
• Blood Reservoir: Liver stores 10-15% of total blood volume.
• Lymph Production: Produced from hepatocytes, helps transport proteins and water.

Section 3.9: Liver Chemistry

• Abnormal blood work leads to ultrasound exams.
• Blood tests determine hepatocellular vs. obstructive disease.
• Liver Function Tests (LFTs): Evaluate hepatocyte function, include ALT, AST, ALP, GGT, LDH, AFP.
• Liver Enzymes: ALT/AST indicate cellular damage; ALP, GGT, LDH check for liver disease signs.
• Prothrombin Time: Measures blood clotting efficiency.
• Albumin: Key protein for fluid balance, abnormal when low.
• AFP: Marker for liver cancer.

Section 3.10: Ultrasound of the Liver

• Normal ultrasound: Homogenous, smooth, fine-grained liver parenchyma.
• Echogenicity: Compared with kidneys (darker) and pancreas (brighter).
• Measurements: Liver size assessed but CT is preferred.
• Key Structures: Diaphragm, ligaments (teres, venosum), vessels (portal and hepatic veins).
• Vascular Structures: Portal triad, main hepatic artery, portal veins, hepatic veins.
• Identification tips: Portal veins (thick, echogenic walls, horizontal), Hepatic veins (thin walls, vertical).
• Liver Protocol: Includes images from lateral to medial and superior to inferior.
• Patient Prep: NPO 6-8 hours, correct transducer choice based on patient habitus.

• End of liver lecture covers anatomy, physiology, and ultrasound appearance.
• Importance of understanding liver’s role and structure for accurate diagnosis and imaging.