How to evaluate lower extremity stents and bypass grafts on ultrasound

Check out Medmastery’s tips and tricks for assessing leg stents and bypass grafts with duplex ultrasound.
Last update26th Feb 2021

Oftentimes, patients will have stents or bypass grafts placed as part of a treatment, so it’s important to be able to recognize them on ultrasound. Let’s dive into how to find and evaluate stents and bypass grafts on duplex ultrasound.

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Lower extremity stents on duplex ultrasound

Finding stents

On ultrasound, stents appear with bright and echogenic borders. Stents are most easily recognized at their proximal attachment.

Occasionally, it can be difficult to find and evaluate stents for patency due to the presence of calcific shadowing. The calcific shadowing is from atherosclerotic plaque that is pushed up against the walls of the artery.

Figure 1. Stents can be recognized on ultrasound by their bright and echogenic borders. Sometimes, calcific shadowing from atherosclerotic plaque can make stents difficult to identify, as demonstrated in this superficial femoral artery stent.

When off-axis, you can usually recognize a stent on ultrasound by its mesh pattern.

Figure 2. A stent can often be recognized on ultrasound by its characteristic mesh pattern.

Check out this short video snippet from our Ultrasound Masterclass: Arteries of the Legs Course to see how to identify a stent by its mesh pattern:

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Evaluating stents

The evaluation of a stent follows a standard protocol where a series of velocities are measured in seven key locations:

  1. Just proximal to the proximal attachment (e.g., inflow).
  2. Within the proximal attachment.
  3. In the proximal portion of the stent.
  4. In the middle of the stent.
  5. In the distal portion of the stent.
  6. Within the distal attachment.
  7. Just distal to the distal attachment (e.g., outflow).

The inflow velocity taken just proximal to the proximal attachment serves as the reference velocity. The velocities are then used to assess the degree of obstruction within the stent.

Figure 3. When evaluating a stent on ultrasound, start by taking the velocity just proximal to the proximal attachment of the stent.

Lower extremity bypass grafts on duplex ultrasound

Finding synthetic bypass grafts

Synthetic bypass grafts (BPGs) are usually easy to recognize on ultrasound. A synthetic BPG looks like a vessel with the same color fill and waveforms as a normal, healthy artery. But, it has patterned edges. Bypass grafts in the superficial femoral artery (SFA) often have a more superficial path compared to the SFA.

Bypass grafts are examined the same way as stents. The only difference is that we use slightly different terminology. Instead of attachments, we use the terms proximal anastomosis and distal anastomosis for the ends of the graft.

Figure 4. A synthetic bypass graft looks like a healthy vessel on duplex ultrasound and has normal waveforms. But, it can be identified by its patterned edges.

Finding autologous bypass grafts

If the graft is autologous (e.g., taken from the patient’s body) from a reversed saphenous vein, there is nothing remarkable about the wall’s appearance. In this case, it is best identified by its pulsating color and location down the length of the medial thigh. In some rare cases, bypass grafts can run down the outer thigh to the anterior tibial artery.

Figure 5. An autologous bypass graft looks just like a normal, healthy vessel on two-dimensional and color flow ultrasound images. It can be identified by its pulsating color and location down the length of the medial thigh.

Some surgeons tend to place the graft in the native artery’s anatomical location—which can be confusing at first. Sometimes you can see the diseased vessel, but it might be difficult to see if the vessel is chronically occluded.

It’s easiest to locate the bypass graft at its proximal anastomosis, which is often in the groin. Once identified, follow the graft continuously like you would with a non-bypassed artery. If you get lost, go back in into a transverse orientation with color to relocate the vessel.

Evaluating bypass grafts

The evaluation of a bypass graft follows the same standard protocol that is used for stents. Measure a series of velocities in seven key locations:

  1. Just proximal to the proximal anastomosis.
  2. Within the proximal anastomosis.
  3. In the proximal portion of the graft.
  4. In the middle of the graft.
  5. In the distal portion of the graft.
  6. Within the distal anastomosis.
  7. Just distal to the distal anastomosis.

The inflow velocity taken just proximal to the proximal anastomosis is the reference velocity. The velocities are then used to assess the degree of obstruction within the bypass graft.

That’s it for now. If you want to improve your understanding of key concepts in medicine, and improve your clinical skills, make sure to register for a free trial account, which will give you access to free videos and downloads. We’ll help you make the right decisions for yourself and your patients.

Recommended reading

  • Aboyans, V, Criqui, MH, Abraham, P, et al. 2012. Measurement and interpretation of the ankle-brachial index: a scientific statement from the American Heart Association. Circulation126: 2890–2909. PMID: 23159553
  • Cervin, A, Wanhainen, A, and Björck, M. 2020. Popliteal aneurysms are common among men with screening detected abdominal aortic aneurysms, and prevalence correlates with the diameters of the common iliac arteries. Eur J Vasc Endovasc Surg59: 67–72. PMID: 31757587
  • Cleveland Clinic. 2021. Leg and foot ulcers. Cleveland Clinichttps://my.clevelandclinic.org
  • Cleveland Clinic. 2021. Marfan syndrome. Cleveland Clinichttps://my.clevelandclinic.org
  • Cleveland Clinic. 2021. Popliteal artery entrapment syndrome (PAES). Cleveland Clinichttps://my.clevelandclinic.org
  • Cleveland Clinic. 2021. Statin medications & heart disease. Cleveland Clinichttps://my.clevelandclinic.org
  • Collins, L and Seraj, S. 2010. Diagnosis and treatment of venous ulcers. Am Fam Physician81: 989–996. PMID: 20387775
  • Høyer, C, Sandermann, J, and Peterson, LJ. 2013. The toe-brachial index in the diagnosis of peripheral arterial disease. J Vasc Surg58: 231–238. PMID: 23688630
  • Jaoude, WA. 2010. Management of popliteal artery aneurysms. SUNY Downstate Department of Surgeryhttp://www.downstatesurgery.org
  • Johns Hopkins Medicine. 2021. Aneurysm. Johns Hopkins Medicinehttps://www.hopkinsmedicine.org
  • Kassem, MM and Gonzalez, L. 2020. “Popliteal artery aneurysm”. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. https://www.ncbi.nlm.nih.gov
  • Moxon, JV, Parr, A, Emeto, TI, et al. 2010. Diagnosis and monitoring of abdominal aortic aneurysm: current status and future prospects. Curr Probl Cardiol35: 512–548. PMID: 20932435
  • Richert, DL. 2016. Gundersen/Lutheran Ultrasound Department Policy and Procedure Manual. Gundersen Health Systemhttps://www.gundersenhealth.org
  • Rivera, PA and Dattilo, JB. 2020. “Pseudoaneurysm”. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. https://www.ncbi.nlm.nih.gov
  • Stanford Medicine 25. 2021. Measuring and understanding the ankle brachial index (ABI). Stanford Medicine 25https://stanfordmedicine25.stanford.edu/
  • Teo, KK. 2019. Acute peripheral arterial occlusion. Merck Manuals Professional Editionhttps://www.merckmanuals.com
  • The Regents of the University of California. 2020. Diabetic foot ulcers. UCSF Department of Surgeryhttps://surgery.ucsf.edu
  • Zwiebel, WJ and Pellerito, JS. 2005. Introduction to Vascular Ultrasonography. 5th edition. Philadelphia: Elsevier Saunders. (Zwiebel and Pellerito 2005, 254–259)

About the author

Elizabeth Tenny, BS RVT RDCS
Registered Vascular Technologist in the Department of Vascular Surgery, Stanford Health Care, USA.
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