Left Lobe of the Liver

The left lobe of the liver is the smaller of the two main anatomical lobes, located in the epigastric and left hypochondriac regions of the abdomen. Although smaller than the right lobe, it is functionally just as important, containing several Couinaud segments and playing a central role in metabolism, bile production, and surgical resections. It has distinct anatomical relationships with the stomach and anterior abdominal wall and contains key landmarks such as the ligamentum teres and falciform ligament. A solid understanding of the left lobe’s structure, vasculature, and segmental anatomy is essential for liver surgery, imaging interpretation, and understanding hepatic disease.

Structure

The left lobe is defined by both surface anatomical landmarks and internal segmentation. Its surface boundary from the right lobe is marked by the falciform ligament, while functional segmentation uses vascular distribution, as defined in Couinaud’s system.

Surface Anatomy

• Anteriorly: The falciform ligament separates the left lobe from the right lobe.

• Visceral surface: The left lobe contacts the stomach (gastric impression), esophagus, and lesser omentum.

• Inferior border: Defined externally by the round ligament (ligamentum teres), which marks the termination of the falciform ligament.

Segmental Division (Couinaud Classification)

The left lobe consists of three segments:

Segment Number Segment Name Location II Lateral superior Located above the portal vein; left lateral lobe, superior to segment III III Lateral inferior Inferior to segment II; forms much of the anterior and inferior left lobe IV Medial segment Subdivided into IVa (superior) and IVb (inferior); sometimes grouped with right lobe on imaging

Segment IV lies anatomically to the left of the gallbladder fossa but is functionally grouped with the left lobe due to portal and arterial supply.

Ligamentous Attachments

• Falciform ligament: Attaches the anterior surface of the left lobe to the anterior abdominal wall and diaphragm.

• Ligamentum teres: Lies in the free edge of the falciform ligament; a remnant of the fetal umbilical vein.

• Lesser omentum: Attaches to the visceral surface of the left lobe and connects it to the stomach and duodenum.

Location

The left lobe lies mainly in the epigastric and left hypochondriac regions. Its anterior surface lies beneath the left hemidiaphragm, and it may reach the midclavicular line on the left side. It is generally smaller than the right lobe but more elongated and flattened in shape.

Topographic Relations

• Anterior: Anterior abdominal wall and diaphragm

• Posterior: Lesser omentum and caudate lobe

• Inferior: Lesser curvature of the stomach and pylorus

• Left: Contacts the fundus and body of the stomach

The left lobe overlaps the stomach in imaging, particularly in cross-sectional CT and MRI, and is in close proximity to the abdominal esophagus and left gastric artery.

Function

The left lobe performs the same functions as the rest of the liver, including metabolic, synthetic, storage, and excretory roles. Although smaller in size, its segments are often favored for partial liver donation due to favorable vascular anatomy and accessibility.

Metabolic and Synthetic Functions

• Regulation of glucose, amino acids, and lipid metabolism

• Synthesis of plasma proteins including albumin and coagulation factors

• Detoxification of drugs, hormones, and metabolic waste products

Bile Production

• Secretes bile into canaliculi leading to segmental bile ducts

• Left hepatic duct drains bile from segments II–IV

Storage and Immunological Role

• Storage of glycogen, iron, copper, and fat-soluble vitamins

• Phagocytic activity via Kupffer cells filtering blood from the portal vein

Clinical Relevance

The left lobe is commonly involved in focal liver lesions, segmental resections, and transplant procedures. Segment II or III are often used in living-donor liver transplants due to their accessible location and vascular independence.

Resections and Surgery

• Left lateral sectionectomy: Removal of segments II and III; commonly done for benign tumors or in pediatric liver transplantation.

• Left hepatectomy: Removal of segments II, III, and IV; performed for malignancies such as intrahepatic cholangiocarcinoma or metastases.

Imaging Landmarks

In cross-sectional imaging:

• Segment II lies superiorly and laterally and is easily visible above the portal bifurcation.

• Segment III lies inferior to segment II and anterior to the stomach.

• Segment IV lies medial and may abut the gallbladder fossa.

Pathological Conditions

• Focal nodular hyperplasia (FNH): Common in the left lobe due to rich arterial supply.

• Liver metastases: Often appear in segment IV due to its central location and vascular convergence.

• Hepatic adenoma: May develop in women on long-term estrogen therapy; left lobe lesions are often amenable to resection.