Vascular access
Fistula stopped working: what to do and how it can be saved
When the thrill (the vibration felt over the fistula) of a fistula that was working well disappears, the fistula has almost always thrombosed: the blood has clotted inside it. In most cases, the cause is a stenosis, a narrowing that had already been reducing the flow. Many fistulas can be saved by removing the clot and treating the stenosis (narrowing), surgically or with a catheter, and the chances are better the sooner treatment is carried out. That is why a fistula that has stopped working should be assessed by the vascular surgeon as soon as possible.
How to tell if the fistula has stopped working
A working fistula has a continuous thrill, felt with the hand, and a bruit, heard with a stethoscope. The signs that it has stopped are:
- the thrill has disappeared or is much weaker than usual;
- the fistula vein has become hard, sometimes painful, like a cord under the skin;
- at the session, the team cannot needle the fistula or gets no flow from it.
If the thrill has gone, seek care the same day
- Do not wait for the next haemodialysis session to report it.
- Tell your dialysis unit and the vascular surgeon who follows your access.
- If you have them, bring the latest Doppler scan or report on the fistula and a list of your medicines.
The sooner the clot is removed, the better the chance of saving the fistula and avoiding a catheter. If you need this assessment, contact our team by WhatsApp or phone and say that it is urgent.
Signs that the fistula may soon stop working
Thrombosis is usually the end of a problem that was already giving warning signs. Tell the team if you notice:
- bleeding that takes longer than usual to stop after the needles are removed;
- high venous pressure on the machine or low flow during sessions, reported by the dialysis team;
- needling becoming more and more difficult;
- the thrill turning into a strong pulse, like a beat, instead of a continuous vibration;
- swelling of the arm, shoulder or face on the fistula side.
These signs suggest a stenosis. Treated before thrombosis, it can usually be corrected with a simpler procedure, and the fistula never stops working.
Why the fistula stops working
The most common cause is stenosis (narrowing) of the fistula vein. High flow and repeated needling make the vein wall thicken in some places. The narrowing reduces the flow until the blood clots.
Other contributing factors:
- A drop in blood pressure, during or after dialysis, from dehydration, diarrhoea or removing a lot of fluid in the session.
- Compression of the fistula: sleeping on the arm, tight clothing or watches, or pressing too long or too hard after the needles are removed.
- Haematomas from difficult needling.
- Infection and clotting disorders, which are less common.
Can the fistula be saved?
Often, yes. Vascular access guidelines recommend treating a thrombosed fistula as soon as possible. In the first hours and days, the clot is still fresh and comes out more easily. As the days go by, it hardens and sticks to the vein wall, and the chances of rescue fall. In general, we treat fistulas that have been blocked for up to 14 days.
Saving the fistula is worth it: it preserves an access that is already working and the veins for the future, and it avoids or shortens the time on a catheter.
How it is treated
Treatment has two goals: removing the clot and correcting the cause, which is almost always the stenosis. Removing the clot without treating the narrowing makes the fistula stop again.
| Technique | How it is done | Strengths |
|---|---|---|
| Surgical thrombectomy | Through a small incision in the skin and the front wall of the fistula, the clot is removed with a balloon-tipped catheter (Fogarty catheter) | Allows the join between artery and vein to be redone slightly higher up when the problem is next to the anastomosis, or to be combined with angioplasty |
| Endovascular thrombectomy | Through a puncture, without an incision, using catheters that aspirate or break up the clot under X-ray guidance | Through the same access, treats narrowings along the vein and in the central veins in the same procedure |
| Balloon angioplasty | A balloon is inflated inside the narrowing to widen it; a stent is sometimes needed | Corrects the cause; accompanies both techniques above |
Guidelines do not single out one technique as best for every case. The choice depends on where the problem is, the type of fistula and the team's experience, and the techniques are often combined in the same procedure.
- AssessmentPhysical examination and Doppler show how far the clot extends and where the narrowing is.
- Clot removalSurgically, with a catheter or both.
- Treating the causeAngioplasty of the narrowing, revision of the anastomosis or, sometimes, a stent.
- Flow checkThe thrill returns, and the flow is checked before the procedure ends.
- Back to haemodialysisAs a rule, the fistula can be used at the next session.
The procedure is usually done under local anaesthesia, sometimes with sedation, and in most cases the patient goes home the same day. It can be done in an operating theatre with a C-arm (mobile X-ray) or in the catheter lab. Patients should be fasting whenever possible and, as a rule, the fistula can be used at the next haemodialysis session.
If the fistula cannot be saved
When the clot is old or the vein is badly damaged, rescue is not always possible. In these cases, a new access is planned: a new fistula higher up the same arm or in the other arm, or a graft. Until the new access can be used, haemodialysis is done through a catheter.
Doppler mapping defines the best option and preserves the veins that may still be useful in the future.
How to prevent it
Day to day
- Feel the thrill every day, morning and evening. You are the first to notice a change.
- Tell the dialysis team about any warning sign, even if the fistula is still working.
- Do not sleep on the fistula arm, and avoid watches, bracelets and tight clothing on that arm.
- After the session, pressure on the needle sites is applied by the nursing team and should stop the bleeding without stopping the thrill.
- Follow your nephrologist's advice on fluids and dry weight, to avoid drops in blood pressure.
At the dialysis unit, examining the fistula at every session and watching venous pressure and flow help to find a stenosis before thrombosis. When there is suspicion, Doppler confirms it, and the narrowing can be treated in advance. General fistula care is covered in the guide to the arteriovenous fistula.
Frequently asked questions
How long do I have to seek help if my fistula has stopped working?
Seek help the same day. The sooner the clot is removed, the better the chance of saving the fistula. After a few days, rescue becomes harder and, after 14 days, it is almost impossible and usually not advised.
Will I need a catheter?
Not always. If the fistula is unblocked in time, it can be used again soon. If the dialysis session cannot wait or rescue is not possible, a catheter is used temporarily.
Does the treatment hurt?
It is done under local anaesthesia, sometimes with sedation. There may be mild discomfort at the site afterwards, controlled with simple painkillers.
Can the fistula stop working again?
Yes. That is why treatment corrects the cause as well as removing the clot, and the fistula continues to be followed up. Further procedures over the years are common and are part of keeping an access working.
Does taking an anticoagulant stop the fistula from clotting?
In general, no. Anticoagulants are not used routinely to prevent fistula thrombosis. They are kept for specific situations, decided with the nephrologist and the vascular surgeon.
References
- Lok CE, Huber TS, Lee T, et al. KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update. Am J Kidney Dis. 2020;75(4 Suppl 2):S1–S164. doi:10.1053/j.ajkd.2019.12.001
- Schmidli J, Widmer MK, Basile C, et al. Vascular Access: 2018 Clinical Practice Guidelines of the European Society for Vascular Surgery (ESVS). Eur J Vasc Endovasc Surg. 2018;55(6):757–818. doi:10.1016/j.ejvs.2018.02.001
About the author
Dr. Pedro Mellucci is a vascular surgeon in Presidente Prudente, Brazil, dedicated to vascular access for haemodialysis and chemotherapy: fistulas, grafts and catheters.
Meet Dr. Pedro Mellucci →