Normal Umbilical Vein Diameter on Ultrasound and CT
The paraumbilical vein is a vestigial channel running within the falciform ligament that connects the left portal vein to the anterior abdominal wall venous plexus. In healthy adults it is either obliterated or remains as a thin fibrous cord measuring less than 3 mm in diameter. Accurate measurement is clinically important because recanalization of this vein is a well-recognized marker of portal hypertension.
Normal Reference Values
| Measurement |
|---|
| <3 mm |
Clinical Significance
A paraumbilical vein diameter of 3 mm or greater, particularly when accompanied by detectable flow on Doppler interrogation, indicates recanalization and is strongly associated with portal hypertension. Recanalization occurs as portal pressure rises and collateral pathways decompress the portal system toward systemic veins, producing the clinical stigma known as caput medusae when superficial abdominal wall veins become visibly dilated.
Identifying a patent paraumbilical vein carries important diagnostic and prognostic implications. It supports the diagnosis of clinically significant portal hypertension and may influence decisions regarding variceal surveillance, transjugular intrahepatic portosystemic shunt (TIPS) planning, or surgical approach. A key pitfall is confusing the paraumbilical vein with a hepatic or portal venous branch; Doppler waveform analysis and tracing the vessel to the falciform ligament help confirm identity.
- Liver cirrhosis with portal hypertension
- Portal vein thrombosis with cavernous transformation
- Budd-Chiari syndrome
- Non-cirrhotic portal hypertension (e.g., nodular regenerative hyperplasia)
- Congestive heart failure with elevated hepatic venous pressure
Reference: Gibson RN, Gibson PR, Donlan JD et al. Identification of a patent paraumbilical vein by using Doppler sonography: importance in the diagnosis of portal hypertension. AJR Am J Roentgenol. 1989;153(3):513-6.
Imaging Notes
Ultrasound: Gray-scale sonography in the transverse and sagittal planes through the upper abdomen is used to identify the paraumbilical vein running within the echogenic falciform ligament. Color and spectral Doppler should always be applied — hepatofugal (away from the liver) flow with a continuous venous waveform confirms recanalization. Measurements should be taken perpendicular to the vessel’s long axis at its widest visible point.
CT: On contrast-enhanced CT (portal venous phase), the recanalized vein appears as a tubular enhancing structure in the falciform ligament. Multiplanar reformats aid in tracing the vessel from the left portal vein to the umbilicus. Diameter is measured on an axial or reformatted image perpendicular to the vessel axis. CT additionally allows assessment of other portosystemic collaterals, splenomegaly, and ascites that collectively support the diagnosis of portal hypertension.