Vessel mapping is performed to identify the best vessels a surgeon can use to create a new vascular access for hemodialysis. Fistula or graft is formed by connecting an artery directly to a vein. It is important to determine which vein is best suited to create into a fistula. This is a crucial first step towards permanent access placement, but it is not just for those new to dialysis. In fact, dialysis patients already receiving treatment can also need a new access at any time.
Vessel mapping can be performed in two ways: through the use of ultrasound, by injecting IV dye to create an angiogram or through a combination of the two methods. Normally, a patient does not experience any discomfort during either of these tests.
NOTE: Nicotine causes blood vessels to constrict. Therefore, you may be asked to avoid all products that contain nicotine (cigarettes, chewing tobacco) for 30 minutes to 2 hours before the test.
Results are then shared with a vascular surgeon and/or your referring physician to plan the creation of a permanent access. It is critical that you complete this very important step in receiving your permanent access as soon as possible. The longer you wait to complete the surgical evaluation, the longer it will be before you have a new permanent access ready for dialysis.
Doppler Ultrasound Vessel Mapping
A Doppler ultrasound test uses sound waves to evaluate the flow of blood through your blood vessels. It allows your doctor to identify the best vessels for creating your fistula. During this test, gel is applied to the skin to promote the passage of sound waves and a handheld instrument (transducer) is passed lightly over the skin above a blood vessel. You will need to lie very still during the procedure. You may hear sounds that represent the flow of blood through your blood vessels. Patients normally do no experience any discomfort during this exam.
A vein imaging with IV dye may also be performed to assess size, depth and functionality of your blood vessels, and to determine best fistula creation.
You will be comfortably positioned in a reclining or laying down position. Dye will be injected through a small IV catheter in your hand and X-ray pictures will be taken to determine the best location for a fistula. Occasionally, when a tourniquet is used, you may feel pressure from this when the vessels are mapped.
Saving the Veins
After identifying the best veins on vessel mapping, your doctor may ask you to “save the veins” in that arm. This will preserve the blood vessels for a future fistula or graft. To save the veins and prevent further damage, you should not allow blood to be drawn or IV’s to be placed in the arm specified by your doctor. You doctor and/or surgeon will advise you on which arm to save.