Ductus venosus
Venous return · SaO2 ~80% Bypasses liver
Narrow, trumpet-shaped shunt from the umbilical vein and left portal vein to the IVC just below the diaphragm. It bypasses the hepatic sinusoids and delivers a fast, well-oxygenated jet that is aimed at the foramen ovale.
Traced from the start
- Placenta
- Umbilical vein
- Ductus venosus
Detail
- Saturation
- ~80%, essentially undiluted umbilical venous blood
- Shunt fraction
- Textbooks quote about half of umbilical venous flow; human Doppler studies show ~30% at 20 weeks falling to ~20% at term, rising again with hypoxia
- Regulation
- Sphincter-like inlet under adrenergic, nitric oxide and prostaglandin control; dilates during hypoxaemia to boost shunting to heart and brain
- Streaming
- Its high-velocity stream stays separate from the slow, desaturated abdominal IVC blood and is directed by the eustachian valve and crista dividens across the foramen ovale
- Closure
- Functionally closed in most infants by 1-2 weeks; fibroses to the ligamentum venosum by ~2-3 months (hover to see)
When it goes wrong
Fetal hypoxaemia or growth restriction on Doppler surveillance
Shunting through the ductus venosus increases to protect heart and brain; an absent or reversed a-wave (atrial contraction) signals cardiac decompensation and is used to time delivery
Reversed ductus venosus a-wave at the 11-13 week scan
Marker of trisomy 21 and major cardiac defects in first-trimester screening
Practise this structure
No question in the bank is tagged to Ductus venosus yet. Questions appear here automatically once one is — the question bank is free to browse in the meantime.