Clotted dialysis access (declot)

A fistula or graft works because blood flows through it quickly all the time. If that flow slows down enough, the blood inside turns into a clot, called thrombosis, and blocks the access completely. When that happens, you cannot have hemodialysis through it.

The most common cause is a stenosis, a narrow segment of scar tissue in the vein that has been building up for weeks or months. Other triggers include low blood pressure, dehydration, pressure on the arm during sleep, a tight bandage after dialysis, or an infection. Grafts clot more often than fistulas.

On the X-ray, a clotted access does not fill with contrast dye, or shows gray, lumpy filling defects where clot sits. After the declot, the channel fills smoothly again from the artery to the chest.

Before a clot, there are often warning signs: a weaker thrill, a pounding pulse, longer bleeding after dialysis, or trouble with needles. These point to a narrowing that can be treated with a planned fistulogram before it clots. Checking your access twice a day is the best protection. See understanding your dialysis access.

A fresh clot is soft and easier to remove. Over days, it hardens and sticks to the vein wall, which makes the declot harder and less likely to work, and it can damage the vein. For most people, the best time to treat is within 24–48 hours, ideally before the next scheduled dialysis.

Speed also protects you. Missing dialysis lets potassium and fluid build up, which can affect your heart and lungs. If the access cannot be reopened in time, you may need a temporary dialysis catheter so you do not miss treatment.

We review your history and examine the access before deciding. If a declot is unlikely to last, we discuss options with your nephrologist and surgeon, such as a surgical revision, a new access, or peritoneal dialysis.

The procedure is done at El Camino Hospital in an interventional radiology suite, with nurses, a radiology technologist and your interventional radiologist. You lie on your back with your arm on an arm board, and we monitor your heart, blood pressure and oxygen. We check your potassium before starting.

1. 1
   Relax and numb

   You receive moderate sedation through an IV and local numbing over the access. Sometimes we place two small punctures, one pointing toward the artery and one toward the heart.

2. 2
   Map the clot

   Through a thin sheath, we inject contrast dye to see where the clot is and how far it extends. We give a blood thinner called heparin to keep new clot from forming.

3. 3
   Remove the clot

   We break up and pull out the clot with a small device, a balloon, or suction, sometimes with a clot-dissolving medicine. The firm plug of clot at the artery connection is pulled free with a small balloon.

4. 4
   Fix the narrowing

   Once flow returns, we find the narrowing that caused the clot and open it with balloon angioplasty, and sometimes a stent.

5. 5
   Confirm and close

   Final pictures confirm good flow and a strong thrill. We remove the sheaths and close the punctures with a small stitch or pressure.

A declot usually takes about 1–2 hours, depending on how much clot there is.

1. First hour
   You rest in recovery while nurses check your access, puncture sites and vital signs. You can eat and drink.
2. Same day
   If you are due for dialysis, your nephrologist may arrange it at the hospital. Otherwise the access can usually be used at your next session. Go home with a driver; no driving, alcohol or important decisions until the next day.
3. First 24 hours
   Leave any small plug or dressing in place until your next dialysis or for 24 hours. After that, you can shower and get the sites wet. A small dissolvable stitch may be present and falls out on its own.
4. Days 1–3
   Soreness and bruising along the arm are normal; the bruise may darken before it fades. Use acetaminophen (Tylenol) and avoid ibuprofen and naproxen.
5. Every day after
   Check your thrill morning and evening. Avoid pressure on the arm, and keep your fluid and blood pressure within your team's targets.

If a puncture site bleeds, stay calm. Press firmly on it with one or two fingers for a full 15 minutes without lifting. Almost all bleeding stops this way; then call us. If it does not stop, keep pressing and call 911. Call 650-404-8445 if the thrill goes away again, your arm swells, pain worsens, or you have a fever above 101°F.

Most recently clotted grafts and many fistulas can be reopened. Because the narrowing that caused the clot tends to return, many people need another balloon treatment within months. Regular checks and early treatment of warning signs help the access last longer.

When a patient calls with a silent access, I want to see them that day, because a clot that is hours old comes out far more easily than one that is days old. During the declot I always look for the reason it clotted, since removing the clot without fixing the narrowing just sets up the next one. I also ask about blood pressure during dialysis and how they sleep, because small habits can make a big difference.

Fabio Komlos, MD, interventional radiologist · About Dr. Fabio Komlos