Surgery Lecture: Liver Anatomy

Liver Anatomy and Blood Supply

• The liver is the largest organ in the body, weighing 1500g, and located in the right upper abdominal cavity beneath the diaphragm and protected by the rib cage.
• The liver receives the majority of its blood supply from the Portal Vein, which delivers 75% of the blood supply, and the remaining 25% from the Hepatic Artery.
• The Portal Vein is formed by the confluence of the Superior Mesenteric Vein and Splenic Vein, and drains the splanchnic blood from the gastrointestinal tract.
• Cantlie's line is an imaginary line that divides the liver into right and left lobes, running from the IVC to the Gall Bladder fossa.

Liver Segments

• The liver is divided into right and left lobes, with the right lobe consisting of segments 5, 6, 7, and 8, and the left lobe consisting of segments 2, 3, and 4.
• Each segment has its own blood supply and biliary drainage, and is functionally independent.
• The caudate lobe (segment 1) drains directly into the inferior vena cava.

Liver Function and Tests

• The liver has a synthetic function, producing approximately 10g of albumin per day, with a half-life of 15-20 days.
• Albumin is a prognostic indicator, and the degree of decrease in albumin corresponds to the degree of liver damage.
• The international normalized ratio (INR) is a measure of the ratio of prothrombin time to mean control prothrombin time.
• Liver function tests (LFTs) are a misnomer, as they measure liver damage or injury rather than function.

Liver Pathology

• Amebic liver abscesses often start with intestinal amebiasis, which may not present with diarrhea.
• The absence of diarrhea does not rule out an amebic abscess.
• The diagnosis of an amebic abscess is confirmed with a CT scan, which shows a non-enhancing and ragged-edge lesion.

Liver Imaging and Diagnosis

• The triple-phase CT scan is the gold standard for liver imaging, with three phases: arterial, portal venous, and washout.
• Each phase helps to differentiate between different types of tumors.
• Hemangiomas are the most common benign liver tumors, and are characterized by peripheral nodular enhancement with progressive centripetal enhancement.
• Focal nodular hyperplasia is a hyperplastic lesion of hepatocytes surrounding a congenital arteriovenous malformation, and is commonly found in females aged 20-50.### Simple Cyst
• Best seen during the arterial phase
• Can differentiate cystic contents using MRI
• Can demonstrate even subtle nodulation along the wall
• Central stellate scars are thought to be formed in response to oxidative stress caused by concomitant arterial hyperperfusion
• Management for symptomatic simple cyst:
  • Part of the cyst wall is resected to allow a permanent drainage
  • High recurrence rate
  • Aspiration: associated with severe recurrence, 20% recurrence rate
  • Medical treatment: Octreotide & Lanreotide, Sirolimus
  • Sclerotherapy: gives immediate relief of symptoms, 92% effective
  • Fenestration: considered with massive hepatomegaly, 22% recurrence rate
  • Hepatic resection: considered with numerous cysts, especially those with spared at least one segment
  • OLT (Orthotopic Liver Transplant): considered in severe cases

Mucinous Cystic Neoplasm

• Complex cyst with thickened walls/nodule
• Septation described as "cyst in cyst" appearance
• Contain bloody or chocolate-like fluid
• With malignant potential over a prolonged period of time (10 years)

Adenoma

• Beta-catenin activated adenoma: most common among men, associated with androgen use
• Imaging:
  • Hypovascular on the early arterial phase
  • Homogenous uptake on the late arterial phase
  • 30% have pseudo-capsule
• MRI with contrast (gadoxectic or ferumoxide)
• Technetium 99 sulfur colloid scan: treatment of choice for bleeding hepatic adenoma

Malignant Lesions

• Hepatocellular Carcinoma (HCC): 5th most common malignancy
• Major risk factors:
  • Viral hepatitis (B or C)
  • Alcoholic cirrhosis
  • Hemochromatosis
  • NASH
• Clinical manifestations:
  • Weight loss
  • Hepatomegaly
  • Tender abdominal mass
  • Jaundice
  • Caput medusae
  • Ascites
• Diagnostic tests:
  • Alpha-fetoprotein (AFP) >400 mg/mL
  • Liver Imaging Reporting & Data System (LIRADS)
• Treatment:
  • Liver resection
  • Liver transplant
  • Transarterial chemoembolization (TACE)
  • Radiofrequency ablation
  • Percutaneous ethanol injection