Ligamentum Teres

The ligamentum teres hepatis, or round ligament of the liver, is a fibrous remnant of the fetal left umbilical vein. It extends from the umbilicus to the liver and resides within the free margin of the falciform ligament. In postnatal life, it no longer functions as a vascular conduit but remains an important anatomical landmark. The ligamentum teres is used surgically as a guide to the left portal structures and also serves as a key structure in segmental liver anatomy. Though small in size, its developmental, topographic, and clinical significance makes it essential in both academic and clinical hepatobiliary anatomy.

Structure

The ligamentum teres is a fibrous cord that originates at the umbilicus and travels superiorly toward the liver. It lies within the inferior free edge of the falciform ligament and courses toward the liver's visceral surface, ultimately entering the liver parenchyma.

Key Anatomical Features

• Length: Varies between 4–7 cm in adults, depending on body habitus
• Width: Typically narrow and cord-like, although it may remain partially patent in some individuals
• Composition: Dense fibrous tissue, sometimes containing residual vascular endothelium or paraumbilical veins

Embryological Origin

During fetal development, the left umbilical vein carries oxygenated blood from the placenta to the fetus. After birth, this vein closes and becomes the ligamentum teres. Closure usually occurs within the first week of life. The corresponding right umbilical vein regresses entirely during fetal life, leaving the left as the dominant vessel.

Relation to the Ligamentum Venosum

The ligamentum teres joins the left branch of the portal vein at the base of the fissure for the ligamentum teres on the visceral surface of the liver. Superiorly, it is continuous with the ligamentum venosum — the fibrous remnant of the fetal ductus venosus, which connected the umbilical vein to the inferior vena cava and bypassed hepatic circulation.

Location

The ligamentum teres travels in the lower part of the anterior abdominal cavity and ascends toward the liver. It is found in a fixed location that helps demarcate anatomical structures on the liver surface and within the peritoneal cavity.

Path of the Ligamentum Teres

1. Begins at the umbilicus, deep to the anterior abdominal wall
2. Ascends within the falciform ligament, which attaches the liver to the anterior abdominal wall and diaphragm
3. Reaches the inferior surface of the liver (specifically, the fissure for the ligamentum teres)
4. Terminates at the umbilical portion of the left portal vein, where it may continue as fibrous tissue within the liver parenchyma

Topographic Associations

• Anteriorly: Lies just beneath the anterior abdominal wall, often seen during laparoscopic procedures
• Superiorly: Joins the left portal triad (left portal vein, left hepatic artery, left hepatic duct)
• Right: Bounded by the quadrate lobe and the gallbladder fossa
• Left: Lies near the surface of the left lobe and close to the origin of the falciform ligament

Function

While the ligamentum teres has no active physiological function in adults, it plays a number of structural and developmental roles:

Fetal Function (as Umbilical Vein)

• Oxygen transport: Carried oxygen-rich blood from the placenta to the fetus
• Portal system connection: Shunted blood through the ductus venosus into the IVC, bypassing the hepatic sinusoids

Postnatal Role

• Anatomical landmark: Marks the anterior boundary between the right and left anatomical lobes of the liver
• Surgical guide: Used to locate the left portal structures during liver surgery or transplant
• Segmental division: Lies within the fissure separating segment IV from segments II and III (Couinaud classification)

Vascular Remnants

Though functionally obliterated, the ligamentum teres may contain recanalizable paraumbilical veins, which can reopen in conditions of portal hypertension, forming part of a collateral pathway.

Clinical Relevance

The ligamentum teres is more than a passive remnant — it has diagnostic and procedural importance in several clinical contexts.

1. Portal Hypertension and Caput Medusae

In portal hypertension, increased pressure in the portal system may lead to recanalization of the ligamentum teres and associated paraumbilical veins. These veins form a portosystemic collateral that connects the portal system with systemic veins around the umbilicus. This can lead to visible venous dilation on the abdominal wall — a condition known as caput medusae.

2. Imaging Landmark

On CT and MRI, the ligamentum teres appears as a fibrous band within the falciform ligament, extending toward the left portal vein. Its presence helps identify:

• The anatomical division between the right and left lobes of the liver
• The fissure for the ligamentum teres on the visceral surface
• The umbilical portion of the portal vein, useful in segmental mapping

3. Surgery and Transplantation

• In liver transplant and segmental resection, the ligamentum teres helps identify the orientation of the left portal structures.
• In cases of hepatomegaly, it may become prominent and assist in liver mobilization during surgery.
• It is sometimes ligated or used as a traction handle during laparoscopic liver resections.

4. Parumbilical Varices and Collaterals

In portal-systemic shunting (either naturally in cirrhosis or surgically via TIPS), the ligamentum teres may carry enlarged veins, visible on Doppler ultrasound or contrast-enhanced CT. These varices can serve as indicators of portal decompression routes.