Digestive system · Abdomen

Liver segment IV !

Liver segment IV is the middle part of the left liver, between the falciform ligament and the gallbladder; its lower part forms part of the gallbladder bed.

Official name: Left medial segment of liver

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What it is

Liver segment IV: the left medial part, including the quadrate lobe.

What it does

Because each segment has its own supply, surgeons can remove one or more segments and leave the rest working.

Key facts

Where

Left medial section between falciform ligament and Cantlie line (gallbladder–IVC); IVa superior, IVb inferior (quadrate lobe)

Blood supply

Branches of left portal vein (umbilical part) and left (or middle) hepatic artery; drains mainly into middle hepatic vein

Nerve

Hepatic plexus (celiac sympathetic and vagal fibres) along its portal pedicle, shared with the whole liver

Function

Functionally part of the left liver though it lies right of falciform ligament; bile to left hepatic duct

Relations

Above

IVa reaches up under the diaphragm to the confluence of the hepatic veins with the inferior vena cava

Below

IVb (quadrate lobe) sits on the porta hepatis, with the gallbladder fossa to its right, the umbilical fissure and round ligament to its left, and the pylorus and first part of the duodenum below

Behind

Liver segment I (caudate lobe), behind the porta hepatis

How to find it

Right of the falciform ligament, under the xiphoid process: IVb (quadrate lobe) is seen from below between the gallbladder and the round ligament, while IVa lies high under the diaphragm near the hepatic vein confluence.

On imaging

On CT or MRI it lies between the middle hepatic vein and the umbilical fissure, split into IVa above and IVb below the portal plane. Focal fatty sparing or fatty change near the falciform ligament and the gallbladder bed is a common pseudolesion here.

Common problems

• Fatty liver disease, very common with obesity and diabetes.
• Hepatitis (viral, alcohol).
• Cirrhosis: scarring that can lead to liver failure and portal hypertension.
• Liver cancer and metastases.

How it is diagnosed

Blood tests (liver enzymes), ultrasound, elastography, CT or MRI, biopsy.

Treatment

• Treat the cause (weight loss, antiviral medicines, stopping alcohol); surgery to remove segments; liver transplant for failure.

Clinical notes

• Its portal pedicles arise from the right side of the umbilical portion of the left portal vein, so a lesion in the umbilical fissure can threaten its blood supply
• In a classic split-liver graft it goes with the extended right graft, yet its inflow comes from the left side, so segment IV can lose blood supply after the split

Development

Its left border, the umbilical fissure, holds the round ligament, the closed fetal left umbilical vein; in portal hypertension small paraumbilical veins along it can reopen.

Related conditions

• Gallbladder cancer

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Educational information, not medical advice. For any symptom, see a health professional.

Its names

Official Latin (TA2)

segmentum mediale sinistrum hepatis TA2 3071

Official Spanish (DeCS)

Segmento IV del hígado DeCS D008099

English (TA2)

Left medial segment of liver

Also called

segment IV of liver

Sources: Terminologia Anatomica (TA2); DeCS; Diagnostic Imaging of the Liver; Anatomy, Abdomen and Pelvis: Liver; 23.6 Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder (OpenStax (Rice University), 2022) · adapted, CC BY 4.0.

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Representative model, for educational purposes only.