“At my last check-up they said the graft was fine and the stent was open. So why can’t the blood pump reach its usual speed during dialysis?”
“Does this mean another operation?”
(Illustrative scenario, not a specific real patient.)
For patients whose arm veins have been used for many years, the dialysis access is often built in segments: a piece of their own vein, a graft and a stent, each covering part of the route. When flow drops in an access like this, the problem is not always the graft or the stent. Sometimes it is a few centimetres of the patient’s own vein right next to the arterial anastomosis. This article looks at that easily overlooked segment.
Key points
- In an access built from segments, trouble often appears at the “hand-offs,” where two materials or two vessel segments meet.
- The native vein next to the arterial anastomosis is short and easy to skip, yet it is the first segment blood passes through after leaving the artery.
- Scanning the whole circuit segment by segment with ultrasound finds the cause more reliably than focusing on the graft alone.
What is a “relay-style” access?
The ideal dialysis access is a fistula made from the patient’s own artery and vein. Over the years, though, forearm and upper-arm veins can narrow, harden or become unusable section by section. The surgeon may then connect the circuit using different materials, for example:
- Native vein: a short segment of the patient’s own vein that is still usable.
- Graft: usually synthetic; biological options also exist, such as a tube made from bovine pericardium.
- Stent: placed in a vein segment that keeps narrowing, to hold it open.
I think of this kind of access as a relay race: the artery starts, the native vein takes the baton, then hands it to the graft and the stent, and finally back to the heart. Each leg can run well on its own, but drop the baton at any hand-off and the whole circuit slows down.
On angiography, a relay-style access looks like this: the bovine pericardial graft on the right joins a stent on the left, which leads back toward the heart. Contrast turns the vessels dark, so changes in calibre and the junctions are easy to see.
Four hand-offs, four common stenosis sites
| Site | Why it narrows | Easy to notice? |
|---|---|---|
| ① Native vein next to the arterial anastomosis (juxta-anastomotic) | Blood leaves the artery under high pressure and turbulence here, which promotes wall thickening | Not really. The segment is short and close to the elbow, and attention tends to go to the graft beyond it |
| ② Graft-to-vein junction | Two materials meet and flow changes character here; a common stenosis site in graft accesses | Fairly easy; usually a focus of routine checks |
| ③ Both ends of the stent | The inside of the stent stays open, but tissue can still grow where it meets the native vessel | Moderate; look specifically at the stent edges |
| ④ Central veins | Previous catheters or long-standing high flow can narrow the large veins near the heart | Hard to see on ultrasound; angiography is often needed |
This article focuses on site ①. It is only a few centimetres long, but it is the first segment blood passes through after leaving the artery. Once it narrows, the graft and stent downstream can only carry the reduced flow that gets through, however open they are.
How do you find which segment is the problem?
1. Feel and look first
A healthy access has a continuous buzzing thrill. If the thrill weakens, or turns into a simple beat (pulse), flow may be obstructed. Where the thrill changes along the arm can hint at where the problem is.
2. Scan segment by segment with ultrasound
I start at the arterial anastomosis and scan all the way through the graft and stent toward the heart, checking diameter and flow in each segment rather than looking only at the graft. That makes it harder to miss the short segment next to the anastomosis.
3. Confirm with angiography when treatment is needed
Once treatment is planned, angiography shows the course of the whole circuit and the length of the stenosis, and also reveals the central veins that ultrasound sees poorly.
Once it is found, how is it treated?
A common approach is balloon angioplasty (PTA): under ultrasound guidance, the access is punctured at a suitable point, a guidewire is passed through the narrowing, and a balloon is used to open it.
Choosing the entry point matters. If the target is next to the arterial anastomosis, the entry point needs some distance from it so the guidewire and balloon have room to work. In a relay-style access, a superficial graft segment of adequate calibre is often a suitable entry. Every access is different, though, and the entry point should follow that day’s vascular map.
After the procedure, the care team usually writes down needle sites, advice on blood pump speed and any precautions for the dialysis unit. From then on, it is the dialysis nurses who look after the access three times a week.
Balloon angioplasty is not a permanent fix. Stenosis can come back, so regular follow-up is needed; if the same site keeps narrowing, the care team may discuss other options.
Three points for healthcare professionals
- When flow drops in a relay-style access, put every hand-off on the differential list. A graft or stent that looks fine does not mean the whole circuit is fine.
- Scan the juxta-anastomotic native segment on its own. It is short, close to the elbow and upstream of the graft, so it is easily passed over.
- Hand over clearly to the dialysis unit afterwards. Needle sites, pump-speed advice and which segment bruises easily all help the next dialysis sessions go smoothly.
For patients: signals worth speaking up about
- Feel your access every day. A weaker thrill, or a buzz that turns into a simple beat, deserves attention.
- The blood pump cannot reach its usual speed, or the machine alarms often.
- Bleeding takes longer to stop after the needles come out.
- The access arm becomes swollen, painful or changes colour.
If you notice any of these, talk to your dialysis nurses and your doctor; don’t wait until you can no longer feel the thrill. If the thrill disappears completely, contact your care team the same day.
About bovine pericardium
Bovine pericardium is treated tissue from the outer lining of a cow’s heart. As a biological material, it can be shaped into a tube to repair or rebuild a blood vessel. We previously described an overseas case of dialysis access reconstruction with bovine pericardium: Bovine Pericardium for Dialysis Access Reconstruction: An International Case.
FAQ
The graft and the stent are both open. Why is flow still too low?
Flow depends on the whole circuit, not only the graft or the stent. Narrowing of the native vein next to the arterial anastomosis, or of the central veins closer to the heart, can also reduce flow. Each segment needs to be checked to find the cause.
Does a juxta-anastomotic stenosis always need surgery?
Not necessarily. Many cases can be treated first with balloon angioplasty; whether another approach is needed depends on the location and length of the stenosis and how often it recurs, as assessed by the care team.
How is a bovine pericardial graft different from a standard graft?
The material differs: bovine pericardium is treated animal tissue, while standard grafts are usually synthetic. Each has its place; the choice depends on your vessels, your access history and insurance rules, and should be discussed with your doctor.
References
- Lok CE, et al. KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update. Am J Kidney Dis. 2020;75(4 Suppl 2):S1–S164. PubMed
- Reconstruction of a Thrombosed Aneurysmal Radio-Cephalic Arteriovenous Fistula with a Tubular Bovine Pericardial Conduit. Kidney Dial. 2025;5(3):46.
This article is general health education. Figure 2 is a de-identified image; the other figures are schematics. All are for teaching purposes only. Every patient is different; please discuss your situation with your own doctor.
