Transjugular Intrahepatic Portosystemic Shunt (TIPS)

Published on 19/07/2015 by admin

Filed under Radiology

Last modified 19/07/2015

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 Controversial whether CTA/MRA is superior to US for TIPS surveillance

image US is primary TIPS surveillance tool
image CTA or MRA indicated if US is technically compromised or equivocal

TOP DIFFERENTIAL DIAGNOSES

• Portal vein occlusion
• Hepatic vein occlusion
• Inferior vena cava occlusion

PATHOLOGY

• Stenosis is usually secondary to intimal fibroplasia within hepatic vein or TIPS itself
• Associated abnormalities

image Hepatic encephalopathy as portal flow bypasses liver

CLINICAL ISSUES

• Maintaining TIPS patency is the major problem

DIAGNOSTIC CHECKLIST

• Consider TIPS malfunction if shunt velocity is < 90 cm/s or portal vein velocity is < 35 cm/s
• Image interpretation pearls

image Low flow is difficult to detect with US
image Confirm occlusion angiographically (CTA, MRA, DSA)
image
(Left) Graphic of TIPS shunt creation shows the hepatic vein punctured within 2 cm of the IVC. The metallic wire TIPS image extends to the right portal vein, adjacent to its junction with the main portal vein.

image
(Right) Image from a TIPS procedure shows the IV catheter image proceeding down the IVC, then penetrating the liver parenchyma to enter the portal vein image. The intraparenchymal tract is dilated with a balloon image. Incidentally noted is a plastic biliary stent image.
image
(Left) Film from the same procedure shows the TIPS itself image deployed with its distal end in the hepatic vein image and its proximal end in the main portal vein image.

image
(Right) Longitudinal color Doppler ultrasound shows the mid portion of a normally patent TIPS image. Although the stent is highly echogenic, it does not obstruct sonographic visualization. Color Doppler indicates brisk flow toward the heart, the expected finding.

TERMINOLOGY

Abbreviations

• Transjugular intrahepatic portocaval shunt (TIPS)

Definitions

• Shunt between main portal vein (PV) and hepatic vein (HV) created with balloon-expandable metallic stent
• Hepatopetal blood flow: Toward liver
• Hepatofugal blood flow: Away from liver

IMAGING

General Features

• Location

image Most common route: Right HV → right PV → main PV
• Size

image 10-12 mm in diameter
• Morphology

image Typically follows curved course through hepatic parenchyma
image Portal end slightly proximal to main PV bifurcation
image Hepatic end located at, or slightly cephalad to, junction of HV and inferior vena cava (IVC)

Ultrasonographic Findings

• Grayscale ultrasound

image Echogenic stent easily seen on grayscale images but does not block sound transmission

– Fabric-covered stent may cause acoustic shadowing soon after placement

image Probably due to gas bubbles trapped in fabric
image May preclude US evaluation of TIPS patency for a few days
image Usually resolves, allowing subsequent US surveillance for TIPS stenosis
image Stent is typically curved but not kinked
image Normally uniform stent caliber
image Hepatic and portal ends “squarely” within veins (best seen on grayscale US)
• Pulsed Doppler

image Portal vein, satisfactory function

– Hepatopetal flow toward heart
– Flow toward shunt in right and left portal branches (occasionally away in left branch)
image Shunt malfunction

– Hepatofugal or bidirectional flow within TIPS
– Peak velocity in portal vein < 35 cm/s
– Flow away from shunt (hepatopetal) in right and left portal branches
image Within shunt, satisfactory function

– Flow slightly turbulent, slight pulsatility, possible slight respiratory variation
– Peak velocity at any location, at least 90 cm/s
– Similar velocity throughout shunt; not > 50 cm/s point-to-point variation
– Similar velocity temporally; not > 50 cm/s change, study-to-study
image Within shunt, malfunction

– Continuous flow (no pulsatility or respiratory change)
– Shunt velocity < 90 or > 250 cm/s at any point
– Temporal drop in velocity ≥ 50 cm/s
– Point-to-point increase in velocity ≥ 50 cm/s indicates focal stenosis
– Focal severe turbulence (post stenosis)
– Absence of flow: Occlusion

image Always confirm angiographically
• Color Doppler

image PV/splenic vein (SV), satisfactory function

– Widely patent, with hepatopetal flow
– Flow toward shunt in right and left portal branches (occasionally away in left branch)
image Within shunt, satisfactory function

– Color flow extends to stent margins
– Uniform, velocity (color scale) throughout shunt
– Mild turbulence
image Within shunt, malfunction

– Visible stenosis, focal or diffuse
– Focal color change indicates high velocity
– Focal severe flow disturbance (post stenosis)
– Absence of flow: Occlusion

image Check with spectral Doppler (more sensitive); always confirm angiographically

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