Residency · Residency · Vascular Surgery

Dialysis Access Complications: Stenosis, Thrombosis, and Steal Syndrome

Overview

Complications related to vascular access are the leading cause of hospitalization among hemodialysis patients, imposing an annual cost exceeding $2 billion in the United States alone. To prolong the lifespan of dialysis access, it is essential to implement surveillance strategies, detect problems early, and intervene promptly. The most common pathway leading to access failure begins with intimal hyperplasia, which causes stenosis and subsequently thrombosis.

Access Surveillance

Clinical Monitoring

Physical examination is crucial and should be performed at every dialysis session. Assessing the thrill over the access provides insight into flow adequacy: a continuous vibration indicates adequate flow, whereas a pulsatile or water-hammer type thrill suggests outflow stenosis. Inspection of the arm and hand is necessary to detect swelling, signs of steal syndrome, aneurysms, or skin changes. Auscultation of the access should reveal a high-pitched, continuous bruit, which is normal; a discontinuous or harsh bruit raises suspicion for stenosis. Dialysis parameters also provide important clues, including elevated venous pressures, difficulty cannulating the access, inadequate clearance as evidenced by low Kt/V, and prolonged bleeding after needle removal.

Duplex Ultrasound Surveillance

Duplex ultrasound is used to measure flow volume (Qa), vein or graft diameter, and velocity ratios. In arteriovenous fistulas (AVF), a flow less than 400-500 mL/min or a reduction greater than 50% suggests significant stenosis. For arteriovenous grafts (AVG), a flow below 600 mL/min is concerning. A velocity ratio exceeding 2:1 at the stenosis site indicates at least 50% stenosis. Surveillance is recommended every 3 to 6 months for AVGs, although the benefit of routine surveillance for AVFs is less clear.

Access Flow Monitoring During Dialysis

Access flow can be monitored during dialysis using ultrasound dilution techniques such as Transonic, thermodilution, or ionic dialysance. A declining trend in access flow is more important than any single absolute measurement. Intervention is typically triggered by a reduction in flow greater than 25% or when flow falls below a critical threshold.

Stenosis

Pathophysiology

Stenosis results primarily from intimal hyperplasia, characterized by smooth muscle cell proliferation and extracellular matrix deposition at sites exposed to hemodynamic stress. In AVFs, stenosis most commonly occurs at the juxta-anastomotic segment (also called the swing point), the cephalic arch, and central veins. In AVGs, over 80% of stenoses develop at the venous anastomosis where the graft meets the vein. Factors such as wall shear stress, compliance mismatch, and turbulent flow drive this process. Central venous stenosis often arises from prior catheterization and affects outflow.

Cephalic Arch Stenosis

This type of stenosis is unique to brachiocephalic AVFs. The cephalic vein makes a sharp turn into the axillary vein, creating a focal area prone to stenosis. It occurs in 30-40% of brachiocephalic AVFs and typically presents with arm swelling, elevated venous pressures, and access dysfunction. Treatment usually involves balloon angioplasty, although recurrence rates are high (50-70% at 6 months). Stent grafts such as Viabahn or Flair improve patency but may limit future treatment options. Surgically, cephalic vein transposition to the axillary vein can bypass the arch and relieve stenosis.

Diagnosis of Stenosis

The gold standard for diagnosing stenosis is a fistulogram or graft study, which involves contrast venography through access puncture. This imaging maps the entire circuit from arterial inflow through the anastomosis, access body, outflow, and central veins, aiding in planning interventions. Duplex ultrasound is also useful for identifying stenosis location and measuring velocities and flow. Clinical signs that prompt investigation include decreased thrill, increased pulsatility, elevated dynamic venous pressures during dialysis (greater than 150 mmHg at 200 mL/min pump speed), decreased Kt/V or urea reduction ratio, prolonged bleeding after needle removal (over 20 minutes), and swelling of the arm or hand.

Treatment of Stenosis

Percutaneous transluminal angioplasty (PTA) is the first-line treatment, involving high-pressure balloon inflation across the stenotic segment. This procedure achieves technical success rates over 90%, with primary patency between 40-60% at 6 months, although restenosis is common. Repeat angioplasty is acceptable for recurrent stenosis. Drug-coated balloons (DCB), which release paclitaxel, have shown emerging evidence of reducing restenosis rates and improving patency compared to plain balloon angioplasty. Stents or stent grafts are reserved for cases with elastic recoil after PTA, recurrent stenosis, or vessel rupture. Covered stents are preferred over bare metal stents in the access circuit but should be used sparingly as they may compromise future surgical revision options. Surgical revision, including patch angioplasty, interposition graft, or jump graft bypassing the stenotic segment, is preferred when stenosis occurs at the anastomotic site and is amenable to surgical correction.

<image>Fistulogram images showing a hemodynamically significant juxta-anastomotic stenosis in an AVF before and after balloon angioplasty with restored luminal diameter and improved flow</image>

Thrombosis

AVF Thrombosis

Thrombosis is less common in AVFs than in AVGs due to the larger vein diameter and better flow. The most common cause is underlying stenosis, but hypotension related to dialysis, compression, and hypercoagulability can also contribute. Early thrombosis occurring within 30 days of access creation often suggests technical errors such as kinking, torsion, or anastomotic problems. Late thrombosis usually results from progressive stenosis.

AVG Thrombosis

Thrombosis is the most common complication of AVGs, occurring at a rate of 0.5 to 2 thromboses per patient-year. It typically arises from venous outflow stenosis causing low flow. Clinically, it may present as an absent thrill, a firm and non-compressible graft, or inability to cannulate the access.

Treatment of Thrombosis

Surgical thrombectomy involves making a transverse incision in the graft (graftotomy) and passing a Fogarty balloon catheter proximally and distally to remove thrombus. The arterial plug, an organized clot at the arterial anastomosis, is cleared. An intraoperative fistulogram is performed to identify and treat any underlying stenosis, often with patch angioplasty or revision of the stenotic segment. This approach allows direct visualization, immediate assessment, and simultaneous revision.

Percutaneous thrombectomy options include pharmacomechanical thrombectomy using devices such as AngioJet or Arrow-Trerotola, aspiration thrombectomy with large-bore catheter suction, and thrombolysis with tissue plasminogen activator (tPA) infusion either by pulse-spray or catheter-directed methods. After clot removal, it is essential to treat the underlying stenosis with angioplasty, with or without stenting. These procedures have immediate technical success rates of 80-95%.

A key principle in thrombosis management is that thrombectomy without addressing the underlying stenosis guarantees rethrombosis. Therefore, fistulogram and stenosis treatment must always be performed during the same session.

<image>Illustration showing percutaneous thrombectomy technique for a thrombosed AV graft with mechanical device removing thrombus, followed by balloon angioplasty of the venous anastomotic stenosis</image>

Steal Syndrome (Dialysis Access-Associated Steal Syndrome — DASS)

Pathophysiology

Steal syndrome occurs when the creation of a low-resistance pathway, such as a fistula or graft, diverts arterial blood away from the distal extremity. Blood preferentially flows into the access rather than continuing distally, resulting in reversal of flow in the distal artery, known as retrograde arterial flow, which steals blood from the hand. This condition is exacerbated by pre-existing arterial disease such as diabetes or peripheral arterial disease (PAD), large anastomoses, and high-flow access.

Incidence

The incidence of steal syndrome varies by access type: it occurs in 1-5% of radiocephalic AVFs, 5-10% of brachiocephalic AVFs, and 5-10% of upper arm AVGs. Risk factors include diabetes, female sex, brachial artery-based access, PAD, and age over 60.

Clinical Grading

Steal syndrome is graded clinically into four stages. Stage 1 involves a pale or blue, cool hand without pain and is generally tolerable. Stage 2 is characterized by pain during dialysis, reflecting ischemic pain exacerbated by further flow diversion from the dialysis machine. Stage 3 involves rest pain even between dialysis sessions, accompanied by motor or sensory deficits. Stage 4 is the most severe, with tissue loss such as ulceration or gangrene of the digits.

Diagnosis

Diagnosis relies on clinical assessment, noting a cool hand, pallor, delayed capillary refill, and diminished or absent pulses distal to the access. Digital pressures and plethysmography reveal reduced digital pressures and flat waveforms. Duplex ultrasound assesses access flow volume, arterial inflow, and distal perfusion. Angiography documents arterial anatomy, collateral development, and stenosis.

Management

Conservative management is appropriate for mild cases (Stage 1-2), involving observation, keeping the hand warm, and avoiding compression. Symptoms may improve as collateral vessels develop, and hand exercises can promote this process.

The Distal Revascularization-Interval Ligation (DRIL) procedure is the gold standard surgical treatment for steal syndrome. It involves ligating the native artery immediately distal to the access anastomosis and creating a bypass from the proximal artery (above the access) to the distal artery (below the ligation) using a vein graft. This eliminates retrograde flow in the distal artery while restoring distal perfusion via the bypass. The DRIL procedure has a success rate exceeding 90% for resolving steal symptoms while preserving access function. Adequate vein conduit is required, which may be harvested from the contralateral leg if necessary.

Banding or plication involves narrowing the access to reduce flow and increase distal perfusion. This simple technique is difficult to calibrate because excessive narrowing can cause thrombosis, while insufficient narrowing may fail to relieve steal. It can be performed using suture plication or a PTFE wrap band. Banding is less predictable than DRIL and may serve as a temporizing measure.

Revision Using Distal Inflow (RUDI) entails ligating the access at its existing proximal anastomosis and creating a new anastomosis to a more distal, smaller artery, such as the radial artery instead of the brachial artery. This reduces access flow while maintaining function and is effective for high-flow steal.

The Minimally Invasive Limited Ligation Endoluminal-Assisted Revision (MILLER) technique uses endovascular banding with a balloon-guided approach. An angioplasty balloon is inflated within the access to calibrate narrowing while monitoring distal perfusion. This method is minimally invasive but has limited long-term data.

Proximalization of the Arterial Inflow (PAI) involves creating new inflow from a more proximal artery, such as the axillary artery, using an interposition graft. This maintains high access flow while reducing competitive steal from the hand and is used for high-flow steal in upper arm access.

Access ligation is the last resort, reserved for severe steal syndrome (Stage 4) when the patient is not a candidate for revision. It sacrifices the access entirely and is required urgently in cases of ischemic monomelic neuropathy.

<image>Surgical diagram of the DRIL procedure showing ligation of the brachial artery distal to the AVF anastomosis and bypass graft from the proximal brachial artery to the distal brachial artery, restoring hand perfusion while preserving fistula function</image>

Access-Related Aneurysm

True Aneurysm (AVF)

True aneurysms involve progressive dilation of the arterialized vein and are common in long-standing fistulas, especially when repeated cannulation occurs at the same sites. Patients should be monitored for rapid enlargement, skin thinning or ulceration, and signs of impending rupture. Treatment options include surgical plication, partial resection with interposition grafting, or exclusion with bypass. Prevention is best achieved by using the rope-ladder cannulation technique, which distributes puncture sites along the access.

Pseudoaneurysm (AVG)

Pseudoaneurysms arise from perigraft hematomas due to repeated puncture at the same site through a thinned graft wall. They present as expanding, pulsatile masses at the cannulation site. Treatment involves surgical excision of the pseudoaneurysm with interposition graft or patch repair. Emergent repair is necessary if the pseudoaneurysm is rapidly expanding, associated with skin breakdown, or active hemorrhage. Prevention includes rotating cannulation sites and avoiding puncture of aneurysmal segments.

Prophylactic Angioplasty

Prophylactic angioplasty involves treating stenosis detected on surveillance before access dysfunction occurs. This practice is controversial. The FHNS trial, which used access flow-based surveillance combined with preemptive angioplasty, showed no benefit in AVGs compared to clinical monitoring alone. Despite this, most clinicians continue to treat hemodynamically significant stenosis (greater than 50% with clinical or hemodynamic abnormalities). Observation alone is reasonable for stenosis without functional impairment.

Clinical Pearls

A pulsatile fistula without a thrill indicates stenosis and should prompt investigation and intervention before thrombosis occurs. The venous anastomosis is the Achilles heel of AV grafts, as intimal hyperplasia here is nearly universal and underlies most graft failures. After thrombectomy, it is imperative to identify and treat the underlying stenosis because thrombectomy alone guarantees rethrombosis. The DRIL procedure is the most reliable surgical treatment for steal syndrome, preserving the access while restoring hand perfusion; mastering this operation is essential. Ischemic monomelic neuropathy differs from steal syndrome; it presents acutely with motor and sensory loss in the hand without skin ischemia and requires immediate access ligation rather than DRIL. Drug-coated balloons represent an emerging tool for treating access stenosis, with early data supporting improved patency over plain balloon angioplasty. Access surveillance programs reduce thrombosis rates but have not been proven to extend overall access survival; their main benefit lies in preventing emergent presentations.

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.
• Schanzer H, et al. Treatment of ischemia due to "steal" by arteriovenous fistula with distal artery ligation and revascularization. J Vasc Surg. 1988;7(6):770-773.
• Beathard GA. An algorithm for the physical examination of early fistula failure. Semin Dial. 2005;18(4):331-335.
• Turmel-Rodrigues L, et al. Treatment of stenosis and thrombosis in haemodialysis fistulas and grafts by interventional radiology. Nephrol Dial Transplant. 2000;15(12):2029-2036.
• Dember LM, et al. (FHNS trial) Effect of clopidogrel on early failure of arteriovenous fistulas for hemodialysis. JAMA. 2008;299(18):2164-2171.

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