Interventional Radiology Imaging

What Imaging Should You Order for a Dialysis Fistula with an Absent Pulse and Thrill?

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What Imaging Should You Order for a Dialysis Fistula with an Absent Pulse and Thrill?

It’s 8 AM on a Tuesday when the dialysis unit calls. Your patient, a 67-year-old with end-stage renal disease, has arrived for their scheduled hemodialysis session, but the nurse reports their left arm arteriovenous fistula is “silent.” On your examination, there is no palpable thrill or audible bruit over the access. This is a clinical emergency for the patient’s dialysis lifeline. You need to choose the right initial imaging study not just to diagnose the problem but to guide immediate, access-saving intervention. This article provides a clinical workflow for this specific scenario, grounded in the American College of Radiology (ACR) Appropriateness Criteria. For suspected access thrombosis with an absent pulse and thrill, the ACR rates Fluoroscopy fistulography hemodialysis access area of interest as Usually Appropriate.

Who Fits This Clinical Scenario?

This guidance is for a specific and urgent clinical presentation: a patient with a previously functioning upper or lower extremity hemodialysis access (either an arteriovenous fistula or graft) who now presents with a complete absence of a palpable pulse and thrill on physical examination. This finding is the clinical hallmark of acute access thrombosis, meaning the access is likely occluded by a clot and is non-functional.

It is crucial to distinguish this scenario from related but distinct clinical problems that require a different diagnostic approach:

  • Suspected Dysfunction (Not Thrombosis): If the patient’s access still has a palpable thrill but is malfunctioning—indicated by high venous pressures, low flow rates (Kt/V), prolonged bleeding after cannulation, or difficulty with needle placement—this falls under a different ACR variant. The access is still patent, but likely has a hemodynamically significant stenosis.
  • Failure to Mature: This applies to a newly created arteriovenous fistula that has not developed adequate flow or diameter for cannulation within approximately two months of creation. The workup is different because the primary issue is developmental, not an acute occlusion of a previously working circuit.
  • Suspected Central Venous Stenosis: If the primary sign is swelling or edema of the access extremity, face, or neck, the clinical suspicion shifts toward a central venous obstruction. While this can lead to thrombosis, the initial workup may be tailored differently if the access itself is still patent.

This article focuses exclusively on the patient whose access has gone from functional to silent, signaling acute thrombosis.

What Diagnoses Are You Working Up in This Scenario?

When a dialysis access suddenly loses its pulse and thrill, you are investigating an acute occlusion. However, the underlying cause of that occlusion is just as important as the clot itself, as it will dictate the therapeutic strategy. The differential diagnosis includes several related pathologies that imaging aims to clarify.

The most common and immediate diagnosis is acute access thrombosis. This is the formation of a blood clot that completely obstructs flow within the fistula or graft. It is the direct cause of the absent thrill and represents a critical loss of dialysis access that requires urgent intervention to salvage.

More fundamentally, thrombosis is almost always a secondary event. The most frequent underlying cause is a high-grade stenosis with secondary thrombosis. Over time, neointimal hyperplasia can cause a progressive narrowing within the access circuit, typically at the venous anastomosis or within the draining vein. This stenosis creates turbulent, low-flow conditions that precipitate clot formation. Identifying and treating this underlying lesion is essential for long-term patency after the clot is removed.

A less common but critical consideration is a central venous stenosis or occlusion. A severe narrowing in the subclavian vein, brachiocephalic vein, or superior vena cava can cause poor outflow from the entire arm. This widespread stasis can lead to the thrombosis of an otherwise healthy access. This must be identified, as treating only the peripheral access will fail if the central outflow problem is not addressed.

Finally, stenosis can occur at the arterial anastomosis or in the feeding artery, though this is less common than venous stenosis. Inadequate arterial inflow can also lead to low flow and subsequent thrombosis. A complete diagnostic evaluation must visualize the entire circuit from the artery to the right atrium.

Why Is Fluoroscopy Fistulography the Recommended Study for This Presentation?

For a patient with a thrombosed hemodialysis access, the ACR designates Fluoroscopy fistulography hemodialysis access area of interest as Usually Appropriate. This procedure is the cornerstone of diagnosis and treatment because it serves a dual purpose: it provides a definitive anatomic map of the entire access circuit and serves as the first step in a potential therapeutic intervention, all within the same session.

A fistulogram, also known as a fistulography or accessogram, involves placing a small needle or sheath directly into the thrombosed access and injecting iodinated contrast under live X-ray (fluoroscopy). This allows the interventional radiologist to visualize the arterial inflow, the body of the fistula or graft, the venous outflow, and the central veins leading to the heart. This comprehensive view is critical for identifying not only the location and extent of the thrombus but also any underlying stenoses that caused it. The ability to immediately proceed with treatment—such as pharmacomechanical thrombectomy (clot removal) and angioplasty or stenting of a stenosis—is the primary reason this modality is preferred. It minimizes delay and maximizes the chance of salvaging the access.

Alternative imaging studies are rated lower for this specific, urgent scenario:

  • US duplex Doppler hemodialysis access area of interest is rated May be appropriate. While it is non-invasive and uses no radiation (RRL O 0 mSv), its role in acute thrombosis is limited. It can confirm the absence of flow and may identify the location of the clot, but it often struggles to visualize the central veins and does not provide the detailed roadmap needed to plan a complex intervention. It is a purely diagnostic study, meaning the patient would still need to proceed to fistulography for treatment, causing a delay.
  • CTA extremity area of interest with IV contrast is rated Usually not appropriate. While CTA provides excellent anatomic detail, it requires a separate peripheral IV for contrast administration (which can be difficult in dialysis patients), exposes the patient to radiation and a significant contrast load without a therapeutic component, and can be challenging to time correctly in a low-flow or no-flow state.

The recommended fistulography involves a moderate radiation dose (ACR RRL=☢☢☢, 1-10 mSv), but the benefit of a combined diagnostic and therapeutic procedure overwhelmingly justifies its use in this time-sensitive clinical setting. Once you’ve decided on this procedure, a detailed understanding of the technique is essential. For a deeper dive into procedural specifics, our protocol guide covers the technique, contrast, and reading principles: IR Central Venous Access (PICC, Tunneled, Port).

What’s Next After Fluoroscopy Fistulography? Downstream Workflow

The results of the fistulogram directly guide the subsequent steps, which often occur during the same interventional radiology procedure. The goal is not just to see the problem, but to fix it.

  • If the study is positive for thrombosis and an underlying stenosis: This is the most common finding. The interventional radiologist will proceed with thrombectomy or thrombolysis to remove the clot and restore flow. Once flow is re-established, the underlying stenosis is treated, typically with balloon angioplasty. A stent may be placed if the stenosis shows significant elastic recoil or dissection after angioplasty. The procedure is considered a technical success if brisk flow is restored through the access with no significant residual stenosis.
  • If the study is positive for thrombosis without an obvious stenosis: While less common, thrombosis can sometimes occur due to prolonged compression, dehydration, or a hypercoagulable state. After clot removal, if no flow-limiting lesion is found throughout the entire circuit, the patient may be able to resume dialysis. However, a thorough search for a subtle lesion is critical, as re-thrombosis rates are high if an underlying cause is missed.
  • If the procedure is technically unsuccessful: In some cases, the clot cannot be removed, or a severe, uncrossable stenosis prevents restoration of flow. At this point, the access is declared non-salvageable. The immediate next step is to arrange for placement of a temporary tunneled dialysis catheter so the patient can receive life-sustaining hemodialysis. The patient will then need a consultation with a vascular surgeon to plan for the creation of a new permanent access.

The downstream workflow is almost entirely procedural. The fistulogram is the gateway to therapy, and the findings dictate the complexity and ultimate success of the access salvage attempt.

Pitfalls to Avoid (and When to Get Help)

In managing suspected dialysis access thrombosis, several common pitfalls can compromise patient outcomes. Awareness of these issues can help streamline care and improve the chances of access salvage.

  1. Delaying the Procedure: Time is critical. The longer an access remains clotted, the more organized the thrombus becomes, making it harder to remove. Successful salvage rates decline significantly after 24-48 hours. An absent thrill should be treated as an emergency requiring prompt evaluation by interventional radiology or vascular surgery.
  2. Incomplete Evaluation: Failing to image the entire access circuit is a major error. If a central venous stenosis is the root cause, treating only the peripheral thrombosis will result in rapid re-occlusion. A complete fistulogram must include visualization from the arterial inflow all the way to the superior vena cava and right atrium.
  3. Misinterpreting a Faint Thrill: A very weak or “thready” thrill can be mistaken for an absent one. However, this finding points toward a severe, flow-limiting stenosis rather than complete thrombosis. While still urgent, the therapeutic approach may differ slightly (primary angioplasty vs. initial thrombectomy). Careful physical examination is key.

If there is any ambiguity in the physical exam or if the patient has complex anatomy, a direct consultation with the interventional radiology team before ordering is always the best course of action.

Related ACR Topics and Tools

Navigating imaging decisions for dialysis access requires a clear understanding of the options and their rationale. For a comprehensive overview of all clinical variants related to this topic, from dysfunction to failure to mature, please consult our parent guide. For tools to help with adjacent scenarios, protocol details, and dose considerations, the following resources are available.

Frequently Asked Questions

Why not just start with a Duplex Ultrasound for a thrombosed fistula?

While Duplex Ultrasound is rated ‘May be appropriate’ and can confirm the absence of flow, it has key limitations in this urgent setting. It cannot visualize the central veins well, provides a less detailed map for intervention, and is a purely diagnostic test. The patient would still require a second procedure (fistulography) for treatment, causing delays that reduce the chance of salvaging the access. Fluoroscopy fistulography is preferred because it is both diagnostic and therapeutic in a single session.

How quickly does a patient with a thrombosed access need a fistulogram?

This is considered a procedural emergency. The success rate of salvaging a thrombosed access decreases significantly with time. Most centers aim to perform the intervention within 24 hours of diagnosis. Prompt communication with the interventional radiology or vascular surgery service is critical as soon as the absent thrill is discovered.

What if the patient has a severe allergy to iodinated contrast?

A severe contrast allergy is a relative contraindication. The interventional team will weigh the risks and benefits. Options include a pre-medication protocol with corticosteroids and antihistamines. In rare cases, CO2 can be used as a contrast agent for patients with severe allergies or advanced renal failure where iodinated contrast is absolutely contraindicated, though image quality is often inferior.

What is the difference between this scenario (thrombosis) and ‘dysfunction’?

The key difference is the physical exam. Thrombosis is defined by the complete absence of a pulse and thrill, indicating no flow. Dysfunction implies the access is still patent (has a thrill) but is not working well, with signs like high venous pressures, low flow rates, or prolonged bleeding. The workup for dysfunction also uses fistulography but is typically less emergent than for acute thrombosis.

Can an MRI or MRA be used to evaluate a thrombosed fistula?

No, MRA and MRV are rated ‘Usually not appropriate’ by the ACR for this scenario. They are time-consuming, expensive, and do not offer a therapeutic component. Furthermore, there are concerns about gadolinium-based contrast agents in patients with end-stage renal disease due to the risk of nephrogenic systemic fibrosis (NSF), although this risk is much lower with modern macrocyclic agents.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 30, 2026