Portal vein ultrasound anatomy variations

Portal Vein System

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The portal vein system (also called the hepatic portal system) is a network of veins that collects blood from the gastrointestinal organs and spleen and delivers it to the liver for processing.
The portal vein system is a venous network that carries nutrient-rich, deoxygenated blood from the gastrointestinal tract, pancreas, spleen, and gallbladder to the liver. It allows the liver to metabolize nutrients, detoxify substances, and filter pathogens before the blood enters systemic circulation.

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Normal Portal Vein Anatomy (on Ultrasound)

Origin: Formed by the confluence of the splenic vein and superior mesenteric vein (SMV) posterior to the neck of the pancreas.

Course: Travels superiorly and to the right, behind the first part of the duodenum and head of the pancreas, into the porta hepatis.

Branches:

• Main Portal Vein (MPV) divides into. (right and Left).
• Right Portal Vein (RPV): Further divides into anterior and posterior branches.
• Left Portal Vein (LPV): Often has a U- or J-shaped curve before branching into medial and lateral segments.

Normal Portal Vein Diameter by Age (Ultrasound)

Age Group	Normal Portal Vein Diameter
Neonates (0–1 month)	2.5 – 4.5 mm
Infants (1–12 months)	3.0 – 5.5 mm
Children (1–10 years)	4.0 – 7.0 mm
Adolescents (11–18 years)	6.0 – 9.0 mm
Adults (18+ years)	Up to ~13 mm (normal upper limit)
With deep inspiration	May transiently reach ~16 mm

Portal Vein Doppler Normal Ranges

Parameter	Normal Range	Notes
Portal Vein Diameter	≤ 13 mm	May transiently increase with inspiration
Portal Vein Velocity (PSV)	20 – 40 cm/s	Steady, monophasic hepatopetal flow
Portal Vein Flow Direction	Hepatopetal	Should always flow toward the liver
Portal Vein Pulsatility Index (PI)	< 0.5	Higher values may indicate right heart dysfunction or portal hypertension
Portal Vein Resistive Index (RI)	N/A	RI not typically measured in PV; applies more to hepatic arteries

Parameter Descriptions

PSV (Peak Systolic Velocity): Highest flow speed during systole.

RI (Resistive Index):

PI (Pulsatility Index):

Hepatopetal = toward liver; Hepatofugal = away from liver.

Notes:

Measurements are typically taken at the porta hepatis, perpendicular to the vessel.

In portal hypertension, diameter may exceed 13–16 mm in adults.

Portal vein diameter can be affected by hydration, respiration, and body habitus.

Common Portal Vein Variations

1.Trifurcation Pattern (10–15%)

• MPV divides into RPV anterior, RPV posterior, and LPV simultaneously.
• No true right portal vein trunk.
• Can be a pitfall in planning liver surgery or transplantation.

2. Early Branching of RPV (5–10%)

• RPV divides before reaching the hepatic parenchym
• Important in preoperative planning.

3. Quadrifurcation

• Rare; MPV gives rise to four primary branches.
• May complicate segmental anatomy interpretation.

4. Right Posterior Portal Vein Arising Directly from MPV

• Instead of forming a common RPV trunk, the posterior branch comes off MPV directly.

5. Cavernous Transformation

• Not a congenital variant, but a collateral venous network forming due to chronic portal vein thrombosis.
• Appears as multiple tortuous vessels in the porta hepatis region.

Ultrasound Appearance & Considerations

The portal venous system can be recognised on ultrasound as a tubular structure with echogenic walls that enters the liver together with the hepatic artery (HA) at the level of the hepatic hilum (a), and reaches the more distal liver segments. (b) Posterior branch of the right portal vein (RPV); (c) left portal vein (LPV) branches. (c) The caudate lobe can be clearly visualised in this scanning plane (asterisk) between the inferior vena cava (IVC), the ligamentum venosum (LV), and LPV. CBD, common bile duct; EHPV, extrahepatic portal vein.

Clinical Relevance of Variations

Portal Hypertension: Elevated pressure in the portal system, often due to cirrhosis.

Portal Vein Thrombosis: Obstruction of blood flow due to clot.

TIPS Procedure: A shunt between the portal and hepatic vein to reduce portal pressure.

Topic related exam

Portal Vein Ultrasound – MCQ Quiz

Note: If you select English, answer all questions in English.
यदि आप हिंदी चुनते हैं, तो सभी प्रश्न हिंदी में हल करें।

1. Which two veins form the portal vein? 1. पोर्टल वेन किन दो वेनों के मिलने से बनती है?

A. Superior mesenteric and splenic veins / सुपीरियर मेसेंटेरिक और स्प्लेनिक वेन
B. Inferior vena cava / इन्फीरियर वेना कावा
C. Renal vein / रीनल वेन
D. Hepatic artery / हेपेटिक आर्टरी

2. What is the echogenicity of the portal vein wall on ultrasound? 2. अल्ट्रासाउंड पर पोर्टल वेन की दीवार कैसी दिखती है?

A. Echogenic / ईकोजेनिक
B. Hypoechoic / हाइपओइकोइक
C. Isoechoic / आइसोइकोइक
D. Anechoic / एनीकोइक

3. What is the normal flow direction in portal vein? 3. पोर्टल वेन में सामान्य रक्त प्रवाह किस दिशा में होता है?

A. Circular / वृत्ताकार
B. Hepatofugal / हेपटोफ्युगल
C. Reversed / उल्टा
D. Hepatopetal / हेपटोपेटल

4. Which part of the liver does the portal vein supply blood to? 4. पोर्टल वेन लिवर के किस हिस्से को रक्त आपूर्ति करती है?

A. Left lobe / बाएं लोब
B. Right lobe / दाएं लोब
C. Both lobes / दोनों लोब
D. Caudate lobe / काउडेट लोब

5. What is the size of the normal portal vein in adults? 5. वयस्कों में सामान्य पोर्टल वेन का आकार कितना होता है?

A. 8-10 mm
B. 10-12 mm
C. 12-14 mm
D. 14-16 mm

6. What condition can cause portal hypertension? 6. पोर्टल हाइपरटेंशन कौन सी स्थिति में हो सकता है?

A. Cirrhosis
B. Hepatitis
C. Liver cancer
D. All of the above

7. Which of the following is not a cause of portal vein thrombosis? 7. निम्नलिखित में से कौन पोर्टल वेन थ्रॉम्बोसिस का कारण नहीं है?

A. Liver cirrhosis
B. Splenomegaly
C. Bacterial infections
D. Pregnancy

8. How is portal vein thrombosis diagnosed? 8. पोर्टल वेन थ्रॉम्बोसिस का निदान कैसे किया जाता है?

A. CT scan
B. Ultrasound
C. MRI
D. All of the above

9. What is the main role of the portal vein? 9. पोर्टल वेन की मुख्य भूमिका क्या है?

A. Carries blood from the liver to the heart
B. Carries nutrient-rich blood to the liver
C. Carries oxygenated blood to the liver
D. Carries waste products from the liver

10. Which ultrasound finding is typical of portal vein thrombosis? 10. पोर्टल वेन थ्रॉम्बोसिस का सामान्य अल्ट्रासाउंड लक्षण क्या है?

A. Hyperechoic thrombus
B. Anechoic thrombus
C. Normal appearance
D. None of the above

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