What are the management options for a hemodialysis patient with an arteriovenous (AV) fistula that can only handle a flow rate of 120ml/min?

Management of AV Fistula with Flow of 120 mL/min

An AV fistula with flow of only 120 mL/min is severely dysfunctional and requires immediate investigation with fistulography to identify and correct underlying stenosis, as this flow rate is far below the minimum threshold needed for adequate hemodialysis and predicts imminent thrombosis and access failure. 1

Critical Flow Thresholds

Your patient's fistula flow of 120 mL/min falls dramatically below all established functional criteria:

• Normal functioning AVF flow: 700-1,300 mL/min 1
• Minimum for access dysfunction threshold: <500 mL/min 1
• Predictor of pending thrombosis: <300 mL/min 1
• Minimum for adequate hemodialysis: 300-500 mL/min blood pump flow 1

At 120 mL/min, this access cannot sustain the minimum 300 mL/min blood flow required for adequate dialysis delivery, making it functionally unusable and at extremely high risk for thrombosis. 1

Immediate Diagnostic Workup

Proceed directly to fistulography rather than intermediate testing, as the severely reduced flow mandates intervention regardless of other findings. 1

Physical Examination Findings to Document

• Pulse vs. thrill: Conversion from thrill to pulse indicates flows <450 mL/min and confirms low-flow state 1
• Bruit characteristics: Intensification or higher pitch suggests stenosis 1
• Extremity edema: May indicate venous outflow obstruction 1
• Collateral vein development: Common in AVF stenosis due to central venous outflow obstruction 1

Recirculation Assessment

Measure access recirculation using a two-needle urea-based method or nonurea-based dilutional method (never use the three-needle peripheral vein method, which overestimates recirculation). 1

• Any recirculation >10% (two-needle method) or >5% (dilutional method) confirms hemodynamically significant stenosis requiring fistulography 1
• At 120 mL/min flow, recirculation is virtually certain since flow is below typical blood pump speeds 1

Anatomic Considerations for AVF Stenosis

AVF stenoses differ critically from graft stenoses in their location and detection:

• Central location: Stenoses occur at vein bifurcations, pressure points, and venous valves in the outflow tract—not at the anastomosis as in grafts 1
• Collateral development: Prevents marked pressure increases, making venous pressure monitoring less reliable than in grafts 1
• Flow measurement priority: Direct flow measurement is the preferred surveillance method for AVF, unlike grafts where pressure monitoring is more useful 1

Definitive Management Algorithm

Step 1: Fistulography with Intervention Capability

Proceed directly to diagnostic fistulography in an interventional suite prepared for immediate treatment. 1

• Identify stenotic lesions in the venous outflow tract, anastomosis, or arterial inflow 1, 2
• Perform percutaneous transluminal angioplasty (PTA) for identified stenoses during the same procedure 1, 2
• Target post-intervention flow: Aim for >20% increase in access flow to confirm successful intervention 1

Step 2: Post-Intervention Assessment

• Repeat flow measurement within 1-4 weeks to document improvement 1
• Failure to achieve flow >400 mL/min after intervention suggests inadequate correction and requires repeat imaging 3, 4
• Target functional flow: Minimum 600 mL/min for reliable hemodialysis use 1, 3

Step 3: If Intervention Fails or Stenosis is Not Correctable

Consider these options in order of preference:

1. Surgical revision if endovascular approach unsuccessful 1, 2
2. New access creation at alternative site if revision not feasible 1
3. Temporary catheter placement while planning definitive access 1

Common Pitfalls to Avoid

Do not delay intervention waiting for "maturation" when flow is this low—120 mL/min represents failure, not delayed maturation. 1

Do not rely on venous pressure monitoring alone in AVF, as collateral development masks pressure changes despite critical stenosis. 1

Do not use ultrasound as the sole diagnostic modality when flow is this severely reduced—proceed directly to fistulography for diagnosis and treatment in one session. 1

Avoid the three-needle peripheral vein recirculation method, which overestimates recirculation due to cardiopulmonary and regional flow effects. 1

Predictors of Poor Outcome

Several factors predict difficulty achieving adequate flow even after intervention:

• Female sex: Associated with smaller vessel diameter and lower maturation rates 1, 3
• Diabetes mellitus: Increased arterial calcification, particularly in distal vessels 1
• Elderly patients: Higher prevalence of arterial disease affecting inflow 1
• Flow <400 mL/min at 30 days post-creation: Only 62% achieve successful long-term patency without intervention 3

Alternative Access Planning

Given the severity of dysfunction, simultaneously plan for alternative access:

• Contralateral arm evaluation for new AVF creation 1
• Tunneled dialysis catheter placement if fistula salvage attempts fail 1
• Consider AVG if no suitable veins remain for native fistula 1