TIPS evaluation

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TIPS evaluation is useful to ensure that the shunt is working properly and that no stenosis has occurred within the stent. Ultrasound is often used as a first-line modality.

Radiographic features

Ultrasound

The normal TIPS should show color Doppler flow throughout its length. The in-stent velocities are typically higher than in a native portal vein .

Trending stent velocities over multiple exams adds specificity to a single evaluation. If there is a concern for a stenosis based on a combination of abnormal findings, venography can be pursued.

Normal
  • normal TIPS velocity: 90-190 cm/sec
  • normal portal vein velocity before entering the TIPS: ~30 cm/sec
  • phasic waveform
  • the portal vein branches normally reverse their flow into the shunt
Stenosis
  • color Doppler aliasing at the site of the stenosis
  • velocity of >190 cm/sec at a stenotic segment
  • velocity of <90 cm/sec in nonstenotic segments
  • velocity <30 cm/sec in the pre-stent portal vein (accessory sign)
  • complete occlusion: lack of color Doppler flow

Always be sure to thoroughly evaluate the hepatic vein distal to the stent as well.

3D and 4D ultrasound techniques to evaluate TIPS flow volumes are being developed as a possible improvement over using velocities .

Venography

To be added. If you have some interventional radiology experience and would like to add to this article, click "Edit Article" above.

Practical points

  • when using color Doppler ultrasound for evaluation, remember to take angle correction into account to avoid false positives; if there is an area of the TIPS without color flow, make sure the TIPS is not approaching 90 degrees relative to the transducer
  • patency of covered TIPS stents is better than bare metal stents and many centers do not evaluate them on a regular schedule, only when there is a suspicion for stent failure
  • recently placed TIPS stents often contain a small amount of gas in the wall of the stent, so if a baseline ultrasound exam is desired, consider waiting a week for the gas to resorb before imaging