Ultrasound Anatomy of the Liver

Objectives

• Discuss normal ultrasound anatomy of the liver
• Grayscale characteristics
• Vascular supply differentiation (portal vs hepatic veins)
• Segmental anatomy
• Threshold measurements

Anatomical Overview

• Location: Right upper quadrant of the abdomen
• Functional Division: Three lobes
  • Right lobe
  • Left lobe
  • Caudate lobe

Lobe Segmentation

• Right Lobe
  • Divided by the main lobar fissure
  • Anterior and posterior segments
• Left Lobe
  • Divided by the left intersegmental fissure
  • Medial and lateral segments
• Caudate Lobe
  • Posterior aspect
  • Bordered by inferior vena cava (IVC) posteriorly and ligamentum venosum anteriorly
• Renal's Lobe
  • Tongue-like extension of the right lobe's inferior tip
  • Often seen in thin women

Vascular Anatomy

• Hepatic Veins
  • Three main veins: Right, Left, Middle
  • Right Hepatic Vein: Right intersegmental fissure
  • Middle Hepatic Vein: Main lobar fissure
  • Left Hepatic Vein: Left intersegmental fissure

Distinction Between Veins

• Portal Veins
  • Bright echogenic walls (thick collagenous tissue)
  • Intrasegmental
  • Formed by veins draining the intestine, spleen, pancreas, and gall bladder
  • Divides into right and left portal veins at porta hepatis

Fissures and Ligaments

• Fissure for Ligamentum Venosum
  • Separates caudate lobe from lateral segment
• Ligamentum Teres
  • Echogenic structure between medial and lateral segments of left lobe
  • Contains fibrous remnant of umbilical vein
• Main Lobar Fissure
  • Separates right and left lobes
  • Identifies gallbladder fossa

Coronad Anatomy

• Segmental Division
  • Based on portal segments
  • Each segment has its own blood supply, lymphatics, and biliary drainage

Liver Segmentation

• Segments are divided by hepatic veins and portal branches
• Segment 1: Caudate lobe
• Segments 2 & 3: Left superior and inferior lateral segments
• Segment 4: Medial segment of left lobe
• Segments 5 & 6: Caudal right lobe
• Segments 7 & 8: Cephalic right lobe

Echogenicity

• Homogeneous in echogenicity
• Relative Comparison:
  • Hypoechoic/isoechoic to pancreas
  • Hyperechoic/isoechoic to right kidney
  • Hypoechoic to spleen

Clinical Examples

• Beaver Tail: Large left lobe wrapping around spleen
• Differentiation:
  • Vessel visualization
  • Color Doppler

Liver Measurements

• Mid-Clavicular Line Measurement
  • Most common method for liver size evaluation
  • Normal length range varies by body type, BMI, gender
• Average Lengths:
  • General: 14 ± 1.7 cm
  • Men: 14.5 ± 1.7 cm
  • Women: 13.5 ± 1.7 cm
• Enlargement: Length ≥ 16 cm considered enlarged

These notes summarize the key points about the normal ultrasound anatomy of the liver, its vascular structure, divisions, and echogenic characteristics, providing a detailed reference for understanding liver anatomy and measurements in ultrasound imaging.