If you’re receiving dialysis, you may at some point require a vascular ultrasound to visualize your AV fistula or graft. Vascular ultrasound is often the imaging method of choice when it comes to visualizing dialysis accesses. Not only can ultrasound immediately help diagnose a variety of problems with your fistula or graft in real-time with the physician, but it is also comfortable for the patient and has relatively low costs. (i,ii)
Let’s explore the variety of instances of when vascular access ultrasounds may be using during your dialysis experience and what you can expect.
What is Vascular Ultrasound?
Ultrasound is a type of imaging modality that uses sounds waves to visualize your body’s tissues, organs and blood vessels. (i) This is a completely non-invasive type of imaging with no radiation involved. It’s very easily tolerated by most patients.
Vascular ultrasound is specifically performed to visualize and assess the blood vessels. An ultrasound imaging specialist, called a vascular sonographer, places special ultrasound gel on the patient’s skin and uses a small camera probe, called a transducer, to visualize the veins and arteries.
Because of the many benefits and capabilities of vascular ultrasound, it’s used in various ways for dialysis vascular access assessment and/or treatment.
Using Vascular Ultrasound to Prepare for Dialysis
Vessel Mapping Vascular Ultrasound
If you have not already had your AV fistula or graft placed, your physician likely required you to have a vessel mapping prior to surgery. The imaging method used for vessel mapping is a one example of how vascular ultrasound can be used.
If you have not started the dialysis planning process yet, an imaging test commonly referred to as a vessel mapping or vein mapping is required of new dialysis patients. The vascular sonographer takes images of the veins and arteries in your arms to ensure they are of adequate size and depth for future placement of your AV fistula or graft.
Dialysis Access Maturation Vascular Ultrasound
After your AV fistula or graft has been successfully placed, it usually takes several months before a fistula can first be used, and several weeks for a graft. Some physicians might opt to order a vascular ultrasound to calculate how much blood is flowing through your vascular access. This number is called “flow volume.” In addition to the physical evaluation performed by your physician, this volume flow number can help your physician determine if your AV fistula or graft has reached maturation.
Using Vascular Ultrasound for Complications with your Dialysis Access
When you start receiving dialysis treatment, there may be times when your AV fistula or graft isn’t working as well as it should. This could be signaled from decreased flow volume or other factors that are monitored closely by a nurse during dialysis. You may also experience physical symptoms that could indicate a problem with your dialysis access.
When these problems arise, your doctor may order a vascular access ultrasound in order to visualize your fistula or graft and see if there are any problems.
The following are common indications for utilizing vascular access ultrasound:
Concern for Fistula or Graft Malfunctioning
Maturation Problems: If a physician feels that a fistula or graft is taking longer than usual to mature (> 6-8 weeks), he or she may order a vascular access ultrasound to look for any potential problems and calculate the current flow volume.
Flow Volume Problems: If a vascular access is unable to deliver a hemodialysis blood flow rate greater than 400 mL/min, a vascular access ultrasound can be used to visualize any narrowing or possible structural problems with the fistula or graft. (iii)
Loss of thrill: When a dialysis access is created, a palpable thrill, also called a bruit, should be felt. Your healthcare team will palpate this thrill often and should also teach you how to palpate it. A sudden loss of thrill or a weaker thrill can be an indicator something is wrong with the vascular access and an ultrasound may be ordered.
Physical Symptoms
General swelling or edema: If the arm that has your fistula or graft suddenly swells, your physician may order a vascular access ultrasound to look for any blood clots that could be associated with your dialysis access or any of the vessels connected to it. Blood clots can cause severe narrowing of fistulas or grafts, or complete blockage.
The vascular sonographer can also visualize fluid around your AV fistula or graft, which can be an indictor to your physician that there may be an infection. These are typically referred to as peri-graft fluid collections.
Localized swelling: In rare cases, something called a pseudoaneurysm may occur. Also known as a false aneurysm, this is when the blood has leaked out of a blood vessel and is encapsulated by the surrounding tissue. It can occur if the blood vessel wall of your access that didn’t seal properly after cannulation. Your doctor may notice a bulging or localized swelling in the area of concern and will order a vascular ultrasound to assess this particular area as well as the rest of the fistula or graft. (ii,iii)
Using Vascular Ultrasound for Monitoring During Dialysis
In some cases, vascular access ultrasounds can also be used to monitor fistulas and grafts. For example, if a fistula or graft begins to malfunction, a vascular specialist may need to surgically revise the access. After the revision, it is not uncommon for a physician to use vascular access ultrasound to ensure the new fistula or graft is maturing properly. (ii)
In other instances, a particular fistula or graft may prove to be a difficult cannulation. For ease of the access for healthcare providers as well as more comfort for the patient, vascular access ultrasounds can sometimes be used to visualize the blood vessels better to determine the best area for cannulation.
Sources:
Sources:
(i) Radiology Info. Ultrasound-vascular. (February 05, 2019). Retrieved on September 10, 2019 from https://www.radiologyinfo.org/en/info.cfm?pg=vascularus.
(ii) Zamboli, P., Fiorini, F., D’Amelio, A., Fatuzzo, P., & Granata, A. (2014). Color Doppler ultrasound and arteriovenous fistulas for hemodialysis. Journal of ultrasound, 17(4), 253–263. doi:10.1007/s40477-014-0113-6
(iii) American Institute of Ultrasound Medicine. (n.d.). Vascular Ultrasound Examination for Postoperative Assessment of Dialysis Access. Retrieved September 9, 2019 from
https://pubmed.ncbi.nlm.nih.gov/32162362/.
