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Ductus Venosus
The ductus venosus is a temporary fetal vascular channel that directs oxygenated blood from the umbilical vein through the liver toward the inferior vena cava. It allows a substantial portion of placental blood to bypass the hepatic sinusoids and reach the fetal heart rapidly.
RegionAbdomen
SystemCardiovascular System
The ductus venosus is a temporary vascular channel of the fetal circulation that allows oxygenated blood arriving from the placenta through the umbilical vein to pass through the liver toward the inferior vena cava while bypassing much of the hepatic sinusoidal circulation.
It is one of the three major fetal circulatory shunts, together with the foramen ovale and ductus arteriosus. These shunts allow fetal blood to follow pathways adapted to placental gas exchange rather than pulmonary gas exchange.
The ductus venosus is particularly important because it helps rapidly deliver relatively highly oxygenated placental blood toward the fetal heart. After birth, placental circulation ceases, flow through the ductus venosus stops, and the vessel normally closes and becomes the ligamentum venosum.
Location
The ductus venosus is located within the fetal liver.
It forms a vascular pathway between the umbilical venous circulation and the systemic venous circulation, directing blood toward the inferior vena cava.
Basic Anatomical Pathway
The pathway involving the ductus venosus can be simplified as:
Placenta → Umbilical vein → Ductus venosus → Inferior vena cava → Right atrium
This route allows a substantial portion of placental blood to reach the heart without first traversing the entire hepatic microcirculation.
Umbilical Vein
The umbilical vein carries oxygenated, nutrient-rich blood from the placenta toward the fetus.
It enters the fetal abdomen at the umbilicus and courses toward the liver, where its blood can either enter the hepatic circulation or pass through the ductus venosus.
Relationship to the Liver
The fetal liver receives a portion of umbilical venous blood for its metabolic and developmental requirements.
The ductus venosus provides a parallel route that allows another portion of this blood to bypass much of the hepatic sinusoidal network.
Hepatic Bypass
The ductus venosus does not completely exclude the liver from placental blood flow. Rather, it provides a preferential channel through which a substantial fraction of umbilical venous blood can avoid passage through the hepatic sinusoids.
This reduces resistance along the route from the placenta to the central venous circulation.
Connection to the Inferior Vena Cava
Blood passing through the ductus venosus enters the hepatic venous region and reaches the inferior vena cava (IVC).
Within the IVC, this relatively oxygen-rich blood mixes to varying degrees with less oxygenated systemic venous blood returning from the lower fetal body.
Blood Flow Toward the Right Atrium
The inferior vena cava carries the mixed blood superiorly into the right atrium.
The fetal arrangement of venous inflow and intracardiac structures favors preferential streaming of much of the relatively well-oxygenated IVC blood toward the foramen ovale.
Relationship to the Foramen Ovale
The foramen ovale is an opening between the fetal right and left atria.
Much of the relatively oxygen-rich blood entering the right atrium from the inferior vena cava is directed across the foramen ovale into the left atrium.
Distribution to the Left Heart
Blood crossing the foramen ovale enters the left atrium, passes through the mitral valve into the left ventricle, and is ejected into the ascending aorta.
This pathway helps deliver relatively well-oxygenated blood to the coronary arteries and vessels supplying the head and brain.
Preferential Streaming
Fetal circulation does not involve complete mixing of all venous blood within the right atrium.
Anatomical orientation and flow patterns promote preferential streaming of oxygen-rich blood from the inferior vena cava toward the foramen ovale, while blood from the superior vena cava is directed predominantly toward the right ventricle.
Importance of Placental Blood
The placenta performs the gas-exchange function that the lungs will assume after birth.
Oxygenated blood returns from the placenta through the single umbilical vein and enters the fetal circulation through the hepatic region.
Oxygen Content
Blood within the umbilical vein has the highest oxygen content of the major fetal vessels because it has just returned from placental gas exchange.
Some oxygen is lost through mixing as the blood passes toward and through the fetal heart, but preferential flow helps preserve delivery of relatively oxygen-rich blood to critical organs.
Function of the Ductus Venosus
The principal function of the ductus venosus is to provide a low-resistance pathway for placental blood through the fetal liver toward the central venous circulation.
Its functions include:
- Partial bypass of the hepatic sinusoids
- Rapid delivery of placental blood toward the inferior vena cava
- Support of preferential delivery of relatively oxygen-rich blood toward the left heart
- Participation in regulation of blood distribution between the fetal liver and central circulation
Regulation of Ductus Venosus Flow
Blood flow through the ductus venosus is influenced by pressure relationships within the umbilical, hepatic, and central venous circulations.
Its narrow configuration also contributes to the velocity and distribution of blood passing through the fetal hepatic region.
Fetal Liver Perfusion
Not all umbilical venous blood passes through the ductus venosus.
A significant portion perfuses the fetal liver, while the remainder is shunted toward the inferior vena cava. The relative distribution can change according to fetal physiological conditions.
The Three Major Fetal Shunts
| Fetal Shunt | Connection | Main Function |
|---|---|---|
| Ductus venosus | Umbilical venous circulation to inferior vena cava through the liver | Partially bypasses hepatic sinusoids |
| Foramen ovale | Right atrium to left atrium | Bypasses pulmonary circulation at atrial level |
| Ductus arteriosus | Pulmonary arterial system to descending aorta | Allows most right ventricular output to bypass the lungs |
Relationship Among the Fetal Shunts
The three fetal shunts function as components of a coordinated circulatory pattern rather than as isolated structures.
The ductus venosus helps bring oxygenated placental blood to the heart, the foramen ovale directs much of this blood into the left heart, and the ductus arteriosus allows most right ventricular output to bypass the high-resistance fetal lungs.
Fetal Blood Flow Sequence
A major pathway of oxygenated placental blood can be represented as:
Placenta → Umbilical vein → Ductus venosus → Inferior vena cava → Right atrium → Foramen ovale → Left atrium → Left ventricle → Ascending aorta
Blood Returning From the Upper Body
Blood returning from the fetal head and upper limbs enters the right atrium through the superior vena cava.
This relatively less oxygenated blood is preferentially directed through the tricuspid valve into the right ventricle.
Right Ventricular Pathway
The right ventricle ejects blood into the pulmonary trunk.
Because fetal pulmonary vascular resistance is high, most of this blood passes through the ductus arteriosus into the descending aorta rather than flowing through the lungs.
Return to the Placenta
Blood in the descending aorta supplies the lower fetal body and enters the paired umbilical arteries.
The umbilical arteries carry blood back to the placenta, completing the fetoplacental circulatory loop.
Development of the Ductus Venosus
The ductus venosus develops during remodeling of the embryonic vitelline and umbilical venous systems associated with formation of the liver and hepatic sinusoids.
As the liver develops, the original venous channels are extensively reorganized to establish the definitive hepatic and systemic venous pathways.
Umbilical Venous Development
Early embryos possess paired umbilical veins. During development, the right umbilical vein and portions of the left regress.
The persistent left umbilical vein becomes the major vessel carrying oxygenated placental blood into the fetus.
Formation of the Hepatic Venous Pathway
Developing hepatic cords disrupt the vitelline veins and create an extensive network of hepatic sinusoids.
Venous remodeling establishes a direct channel through the liver that becomes the ductus venosus.
Changes at Birth
Clamping of the umbilical cord abruptly terminates placental blood flow.
Because the umbilical vein no longer carries blood from the placenta, flow through the ductus venosus rapidly decreases and normally ceases.
Functional Closure
Loss of umbilical venous flow causes the ductus venosus to become functionally unnecessary.
The vessel constricts and subsequently undergoes anatomical obliteration.
Anatomical Closure
Following cessation of flow, the ductus venosus progressively becomes fibrotic.
Its postnatal remnant forms a fibrous structure within the liver.
Ligamentum Venosum
The adult remnant of the ductus venosus is the ligamentum venosum.
It lies in a fissure on the visceral surface of the liver and marks the former fetal vascular pathway.
Before and After Birth
| Feature | Fetal Life | After Normal Closure |
|---|---|---|
| Structure | Ductus venosus | Ligamentum venosum |
| Function | Shunts placental blood toward the IVC | No vascular function |
| Blood source | Umbilical vein | Umbilical venous flow absent |
| State | Patent vascular channel | Fibrous remnant |
Umbilical Vein After Birth
The intra-abdominal portion of the umbilical vein also loses its placental blood flow after the umbilical cord is clamped.
Its major fibrous remnant becomes the ligamentum teres hepatis, or round ligament of the liver.
Ligamentum Teres and Ligamentum Venosum
The ligamentum teres and ligamentum venosum represent two adjacent remnants of the fetal umbilical venous pathway.
The ligamentum teres marks the former umbilical vein, while the ligamentum venosum marks the former ductus venosus.
Relationship to Liver Anatomy
The ligamentum venosum occupies a fissure on the visceral surface of the liver between the anatomical left lobe and caudate lobe.
Its location remains an important landmark reflecting the arrangement of fetal venous circulation.
Fetal Versus Adult Venous Circulation
| Feature | Fetus | After Birth |
|---|---|---|
| Gas exchange organ | Placenta | Lungs |
| Umbilical vein | Carries oxygenated placental blood | Closes and contributes to ligamentum teres |
| Ductus venosus | Shunts blood toward IVC | Becomes ligamentum venosum |
| Portal circulation | Developing and partially bypassed by fetal shunt | Major venous route through liver |
Ultrasound Visualization
The ductus venosus can be visualized during fetal ultrasonography.
Color Doppler helps identify the high-velocity channel connecting the umbilical venous pathway with the central venous circulation.
Doppler Assessment
Doppler ultrasound can display changes in ductus venosus blood velocity during the fetal cardiac cycle.
The resulting waveform reflects interactions among venous return, atrial pressure, ventricular filling, and cardiac contraction.
Ductus Venosus Waveform
A normal ductus venosus Doppler waveform is pulsatile and changes with phases of the cardiac cycle.
Characteristic components correspond broadly to ventricular systole, early ventricular diastole, and atrial contraction.
Clinical Significance of Doppler Changes
Abnormal ductus venosus flow patterns can occur when fetal central venous pressure or cardiac function is altered.
For this reason, ductus venosus Doppler assessment is used in selected fetal evaluations as part of broader obstetric and cardiovascular assessment.
Absent or Reversed Flow
Marked abnormalities of the ductus venosus waveform, including absent or reversed flow during atrial contraction, can be associated with significant fetal hemodynamic disturbance.
Such findings must be interpreted together with gestational age, other Doppler measurements, fetal anatomy, and the overall clinical context.
Persistent Ductus Venosus
Failure of the ductus venosus to close after birth is uncommon.
Persistent communication can create an abnormal portosystemic pathway in which portal venous blood bypasses the liver and enters the systemic venous circulation.
Congenital Absence of the Ductus Venosus
In some fetuses, the normal ductus venosus is absent and umbilical venous blood follows an alternative route.
The clinical significance depends strongly on where the umbilical vein drains and whether associated cardiovascular or other congenital abnormalities are present.
Portosystemic Connections
Because the ductus venosus normally links the fetal portal-umbilical venous region with the systemic venous circulation, abnormalities involving its persistence or development can produce unusual portosystemic connections.
Imaging is required to define the precise anatomy of these abnormal pathways.
Comparison With the Ductus Arteriosus
| Feature | Ductus Venosus | Ductus Arteriosus |
|---|---|---|
| Location | Within fetal hepatic region | Thorax near pulmonary artery and aorta |
| Main connection | Umbilical venous pathway to IVC | Pulmonary arterial system to descending aorta |
| Main bypass | Much of hepatic sinusoidal circulation | Pulmonary circulation |
| Adult remnant | Ligamentum venosum | Ligamentum arteriosum |
Comparison With the Foramen Ovale
| Feature | Ductus Venosus | Foramen Ovale |
|---|---|---|
| Type | Vascular channel | Interatrial opening |
| Location | Fetal liver | Interatrial septum |
| Flow | Umbilical venous blood toward IVC | Right atrium toward left atrium |
| Main purpose | Partial hepatic bypass | Pulmonary bypass at atrial level |
Key Features of the Ductus Venosus
| Feature | Key Point |
|---|---|
| Structure | Temporary fetal venous channel |
| Location | Fetal liver |
| Blood source | Umbilical vein |
| Destination | Central venous circulation and inferior vena cava |
| Main function | Partial bypass of hepatic sinusoids |
| Blood carried | Relatively oxygen-rich placental blood |
| Closure trigger | Loss of umbilical blood flow after birth |
| Adult remnant | Ligamentum venosum |
Anatomical and Physiological Importance
The ductus venosus is a key component of the specialized fetal circulation. Its position within the liver creates a direct pathway through which a substantial portion of oxygenated placental blood can bypass the hepatic sinusoids and reach the inferior vena cava efficiently.
Its importance extends beyond simple hepatic bypass. The blood delivered through the ductus venosus contributes to preferential streaming through the right atrium and foramen ovale, helping relatively oxygen-rich blood reach the left ventricle, ascending aorta, coronary circulation, and cerebral circulation.
At birth, loss of placental flow makes the ductus venosus unnecessary. Closure of this vessel, together with closure of the foramen ovale and ductus arteriosus, is part of the fundamental transition from fetal circulation dependent on the placenta to postnatal circulation dependent on the lungs.
Published on September 30, 2026
Last updated on September 30, 2026
Last updated on September 30, 2026