No Vibration in Your Fistula? It May Be Blocked

What a normal thrill feels like

In a healthy fistula, lightly touching the skin over the vessel reveals a continuous, even "buzzing" vibration. This thrill is produced as arterial blood flows through the fistula into the vein. With a stethoscope, you can hear a continuous flow sound (bruit). The thrill should be present at all times and should not come and go with position changes.

A weaker thrill may signal narrowing

If the thrill becomes faint or intermittent, or you have to press harder to feel what was once obvious, this often means the fistula is narrowing (stenosis) and blood flow is decreasing. Early narrowing may not affect dialysis right away, but without treatment it can worsen and eventually lead to complete blockage.

A thrill that disappears completely is an emergency

If a thrill you could previously feel suddenly disappears and the area feels no different from the surrounding skin, the fistula may have become acutely blocked and blood flow has stopped. This requires immediate attention—the longer the blockage lasts, the lower the chance of saving the fistula. Contact your care team or go to the emergency department right away rather than waiting for your next dialysis session.

Other warning signs

• Clearly inadequate blood flow during dialysis, with frequent machine alarms
• Bleeding that takes much longer than usual to stop after dialysis
• Unexplained swelling of the fistula arm or unusual coldness
• Skin color changes or significant pain around the fistula

What happens next

When narrowing or blockage is suspected, the care team usually begins with a physical exam (touch and listening), followed by ultrasound or angiography when needed to locate the problem and assess its severity. They will then explain the appropriate treatment to help keep the fistula usable for as long as possible.