Anatomy of the Liver-Liver Ultrasound Perspective

ANATOMY OF THE LIVER- Liver Ultrasound Perspective

Liver Lobes and Segments

1. Lobes:
Right lobe: Largest; located in the right hypochondrium

Left lobe: Extends into the epigastric region

Caudate lobe: Posterior to the left lobe, adjacent to the inferior vena cava (IVC)

Quadrate lobe: Medial segment of the left lobe, near the gallbladder

Couinaud Segmentation: Used for surgical and imaging localization, dividing the liver into eight functionally independent segments, each with its own portal vein, hepatic artery, and bile duct branch.

2. Couinaud Segmental Anatomy (8 Segments)

Liver Segments and Main Landmarks

Segment	Location	Main Landmarks
I	Caudate lobe	Posterior to portal vein, near IVC
II	Left superior lateral	Above left portal vein
III	Left inferior lateral	Below left portal vein
IVa/b	Left medial (superior/inferior)	Medial to falciform ligament
V	Right anterior inferior	Below right portal vein, anterior
VI	Right posterior inferior	Below right portal vein, posterior
VII	Right posterior superior	Above right portal vein, posterior
VIII	Right anterior superior	Above right portal vein, anterior

3. Diaphragm thickness
The normal thickness of the diaphragm around the liver, measured by ultrasound, is between 2.2mm -2.8mm. centimeters in healthy volunteers. A diaphragm thickness of less than 0.2 centimeters at the end of exhalation is considered a sign of diaphragm atrophy.

Thickening fraction is calculated according to the formula = (EIT − EET)/EET × 100.

ANATOMY OF THE LIVER- Liver Ultrasound Perspective

Vascular Anatomy

Portal Vein System

• Formed by the confluence of the superior mesenteric and splenic veins
• Has echogenic walls on ultrasound due to collagenous content
• Enters the liver at the porta hepatis, dividing into right and left branches
• Supplies ~75% of liver’s blood flow

The portal venous system can be recognised on ultrasound as a tubular structure with echogenic walls that enters the liver together with the hepatic artery (HA) at the level of the hepatic hilum (a), and reaches the more distal liver segments. (b) Posterior branch of the right portal vein (RPV); (c) left portal vein (LPV) branches. (c) The caudate lobe can be clearly visualised in this scanning plane (asterisk) between the inferior vena cava (IVC), the ligamentum venosum (LV), and LPV. CBD, common bile duct; EHPV, extrahepatic portal vein.
Hepatic Artery

• Arises from the celiac trunk
• Supplies ~25% of liver’s blood
• Usually seen adjacent to the bile duct and portal vein (the "portal triad")

Hepatic Veins

• Right, middle, and left hepatic veins drain into the IVC
• No echogenic walls; typically seen as anechoic channels converging superiorly

The hepatic veins originate from the periphery of the liver, converging into the inferior vena cava (IVC). LHV, left hepatic vein; MHV, middle hepatic vein; RHV, right hepatic vein.

ANATOMY OF THE LIVER- Liver Ultrasound Perspective

Biliary System

Intrahepatic Bile Ducts

• Run alongside portal vein branches
• Not normally visible unless dilated

The common bile duct (CBD) can be seen as a thin tubular structure with echogenic walls that, in the majority of cases, runs anteriorly and parallel to the portal vein (PV) at the level of the hepatic hilum. The hepatic artery (HA) is often seen at this level in transverse section, hence it is visualised as a small rounded or ovoid structure (depending on the angle of insonation) with echogenic walls between the CBD and the PV.
Extrahepatic Biliary System

• Includes the common hepatic duct, cystic duct, and common bile duct (CBD)
• CBD is often evaluated in the porta hepatis region
• Normal CBD diameter: ≤ 6 mm in adults (can increase with age or post-cholecystectomy)

The gallbladder (GB)-

The gallbladder (GB) is a pear‐shaped structure located in the GB fossa, a depression on the visceral surface of the liver between the right and left lobe. The GB is usually lateral to the second part of the duodenum and anterior to the right kidney (RK). (b) Note is made of the main interlobar fissure (IF) between the portal vein (PV) and the GB.

ANATOMY OF THE LIVER- Liver Ultrasound Perspective

Ligaments and Landmarks

Falciform Ligament

• Divides left and right lobes anteriorly
• Sometimes visible as a thin echogenic line on ultrasound

Ligamentum Teres (Round Ligament)

• Remnant of fetal umbilical vein
• Seen as an echogenic focus within the left lobe

Ligamentum teres (LT) or round ligament takes direct contact with the left branch of the portal vein (LPV). LT runs along the ventral surface of the liver continuing with the falciform ligament (FL) along the dorsal surface of the liver. By changing the plane of insonation from transverse to longitudinal scan view (left to right image) the LT will be seen elongating in full extent to join the FL (right side image).
Ligamentum Venosum

• Remnant of fetal ductus venosus
• Separates the caudate lobe from the left lobe

Ligamentum Venosum

• Remnant of fetal ductus venosus
• Separates the caudate lobe from the left lobe

The boundaries of the caudate lobe

The boundaries of the caudate lobe (asterisk) are defined by the retrohepatic inferior vena cava (IVC), the ligamentum venosum (LV), and the left branch of the portal vein (LPV) that is better seen when imaging in transverse section (left side image).

Introduction of liver ultrasound

Introduction to Liver Ultrasound

Purpose and Clinical Relevance

Purpose:
Liver ultrasound is a non-invasive, cost-effective, and widely accessible imaging modality used to evaluate the liver's structure and detect abnormalities. It is often the first-line imaging technique for assessing liver disease due to its safety (no radiation), real-time capability, and ability to guide interventional procedures.

Clinical Relevance:

• Early Detection of Liver Disease: Identifies early signs of fatty liver, hepatomegaly, or focal lesions.
• Assessment of Liver Size, Shape, and Texture: Helps evaluate hepatomegaly, atrophy, or nodular surface changes.
• Characterization of Liver Lesions: Differentiates benign (e.g., hemangioma, cysts) from malignant lesions (e.g., HCC, metastases).
• Monitoring Chronic Liver Disease: Tracks progression in hepatitis, NAFLD, and fibrosis.
• Guidance for Interventional Procedures: Real-time guidance for biopsies, drainages, and aspirations.
• Evaluation of Vascular and Biliary Systems: Assesses portal vein, hepatic veins, and biliary duct dilation.
• Surveillance in High-Risk Populations: Routine use for cirrhosis, chronic hepatitis B/C.
• Screening in Asymptomatic Patients: Detects incidental findings of early liver disease.

Indications for Liver Ultrasound

• Evaluation of Abnormal LFTs
  • Elevated ALT, AST, ALP, bilirubin
  • Unexplained enzyme abnormalities
• Assessment of Liver Size and Texture
  • Suspected hepatomegaly or atrophy
  • Palpable liver
• Characterization of Lesions
  • Cysts, hemangiomas, adenomas
  • Primary/metastatic tumors
• Cancer Surveillance
  • Cirrhosis
  • Chronic hepatitis B/C
  • NASH
• Chronic Liver Disease
  • NAFLD, alcoholic liver disease
  • Fibrosis or cirrhosis
• Portal Hypertension
  • Splenomegaly, ascites, varices
  • Doppler of portal vein
• Biliary Obstruction
  • Jaundice, RUQ pain
  • Elevated ALP, GGT
  • Gallstones, bile duct dilatation
• Guided Procedures
  • Biopsy, drainage, aspiration
• Follow-up Studies
  • Monitoring known lesions
  • Treatment response (e.g., ablation)
• Infectious or Inflammatory Causes
  • Pyogenic/amebic abscess
  • Hepatitis (viral or autoimmune)
• Pediatric Liver Conditions
  • Neonatal cholestasis
  • Congenital anomalies
  • Metabolic liver disease

Limitations and Contraindications

Limitations:

• Operator dependence
• Small/isoechoic lesions may be missed
• Obesity, gas, or ascites may impair view
• Difficulty distinguishing benign vs malignant lesions
• Limited field of view (deep dome lesions)
• No functional assessment (e.g., perfusion)
• Incomplete view of biliary tree

Contraindications:

• Recent surgery or trauma (pain, dressings)
• Non-cooperative patients (infants, confused)
• Excessive abdominal distension (gas, ascites)

Liver

1. Introduction 100%

Purpose and Clinical Relevance
Indications for Liver Ultrasound
Limitations and Contraindications

2. Anatomy of the Liver 30%

Lobes and Segments
Vascular Anatomy (Hepatic Artery, Portal Vein, Hepatic Veins)
Biliary System
Ligaments and Landmarks

3. Patient Preparation 100%

Positioning & Techniques
Standard Patient Positions (Supine, Left Lateral, Right Lateral)
Scanning Planes in Liver Ultrasound
Systematic Scanning Planes for Liver

4. Technical Assessment 100%

Transducer Selection
Imaging Modes
Machine Settings and Optimization

5. Normal Liver Appearance 30%

Echotexture and Echogenicity
Liver Size and Contours
Portal Triad and Vasculature
Biliary Tree and Gallbladder Overview

6. Liver Pathologies and Diagnostic Clue

1. Congenital and Developmental Disorders

Hepatic Cysts (Simple, Congenital)
Polycystic Liver Disease (PCLD)
Congenital Hepatic Fibrosis
Caroli Disease
Aberrant hepatic veins / accessory fissures

2. Infectious Diseases

Pyogenic Liver Abscess
Amoebic Liver Abscess
Hydatid Cyst (Echinococcosis)
Viral Hepatitis (A, B, C, D, E)
Tuberculous Hepatitis
Fungal Hepatitis

3. Inflammatory and Autoimmune

Autoimmune Hepatitis
Primary Biliary Cholangitis (PBC)
Primary Sclerosing Cholangitis (PSC)
Sarcoidosis of Liver
Chronic Active Hepatitis
Drug-Induced Liver Injury (DILI)

4. Vascular Disorders

Budd-Chiari Syndrome
Portal Vein Thrombosis
Portal Hypertension
Arterioportal Fistula
Hepatic Artery Aneurysm
Passive Congestion

5. Steatosis and Storage Disorders

Non-Alcoholic Fatty Liver Disease (NAFLD)
Non-Alcoholic Steatohepatitis (NASH)
Alcoholic Fatty Liver Disease
Glycogen Storage Diseases
Hemochromatosis
Wilson’s Disease
Amyloidosis

6. Cystic and Biliary Lesions

Simple Hepatic Cyst
Biliary Cystadenoma / Cystadenocarcinoma
Choledochal Cyst
Biliary Hamartomas

7. Benign Tumors

Hemangioma
Focal Nodular Hyperplasia (FNH)
Hepatic Adenoma
Lipoma

8. Malignant Tumors - Primary

Hepatocellular Carcinoma (HCC)
Fibrolamellar HCC
Steatohepatitic HCC
Cholangiocarcinoma (Intrahepatic)
Angiosarcoma
Hepatoblastoma

9. Malignant Tumors - Metastatic

Colorectal Cancer Metastasis
Breast Cancer Metastasis
Pancreatic/Gastric Metastases
Neuroendocrine Tumor Metastases

10. Cirrhosis & Chronic Liver Disease

Alcoholic Cirrhosis
Viral Cirrhosis
Cryptogenic Cirrhosis
Metabolic Cirrhosis
Autoimmune Cirrhosis
Decompensated Cirrhosis

11. Traumatic and Iatrogenic

Liver Laceration
Subcapsular Hematoma
Post-biopsy Hemorrhage
Biloma
Post-Transplant Complications

12. Pediatric Liver Pathologies

Neonatal Hepatitis
Biliary Atresia
Hepatoblastoma
Alagille Syndrome
Glycogen Storage Disorders

13. Interventional and Post-Surgical Imaging 0%

Post-Surgical Liver Imaging
Liver Biopsy Guidance
Percutaneous Drainage of Abscesses
Post-Transplant Evaluation
Post-procedural Complications (Bleeding, Biloma, Leak)

14. Advanced Modalities and Differential Diagnosis 0%

Role of CT, MRI, and MRCP in Liver Pathology
Liver Elastography and Fibrosis Grading
Contrast-Enhanced Ultrasound (CEUS) in Focal Liver Lesions
Differentiating Benign vs. Malignant Lesions Sonographically

15. Case Studies and Quiz Section 0%

Clinical Case Reviews
Image-Based Interpretation Questions
Diagnostic Challenges
Pitfalls and Pearls in Liver Ultrasound Practice