14.1 Pre-Operative Vascular Mapping for Dialysis Access

Plan access for the person, not an automatic hierarchy

Hemodialysis access mapping describes the arteries, veins, and outflow available for a proposed access. The KDOQI 2019 update emphasizes an individualized ESKD Life-Plan that considers dialysis modality, expected duration, transplant possibilities, prior access, patient goals, and future options. “Fistula first in every patient” and “always start at the wrist” are oversimplifications. Preserving future sites matters, but the best access is selected by the treating team for the individual.

Review kidney disease status, dominant arm, prior catheters, pacemakers, surgery, trauma, thrombosis, existing accesses, hand symptoms, and previous mapping. Examine pulses, arm pressures when safe, skin, scars, edema, and visible collateral veins. A history of central venous instrumentation raises concern for outflow disease that a superficial vein measurement alone cannot exclude.

Arterial mapping

Use grayscale, color, and spectral Doppler to assess accessible inflow from the proximal arm through the intended distal vessels. Describe patency, luminal diameter, calcification, focal lesions, waveform morphology, and anatomic variants such as a high-origin radial artery. Record which vessel was measured and where; a single forearm diameter cannot represent the complete inflow pathway.

Measure diameter consistently with light probe pressure and an appropriate image plane. Calcification may cause shadowing and reduce assessment. A small artery, poor distensibility, significant stenosis, or impaired hand perfusion can affect feasibility, but no isolated measurement predicts every outcome. KDOQI does not specify one universal minimum artery/vein diameter for fistula creation; vessels below 2 mm warrant particularly careful evaluation of quality and feasibility.

Palmar circulation

The superficial arch is usually predominantly supplied by the ulnar artery and the deep arch by the radial artery, with variable completeness and connections. A modified Allen or Doppler/photoplethysmographic examination can assess the response to selective compression. Establish a reliable baseline and apply the laboratory's protocol rather than compressing indiscriminately.

If digital waveforms disappear during radial compression and recover when it is released, collateral hand perfusion is concerning under that test. Verify technique and evaluate the remaining circulation. This is not proof that every radial-based fistula will inevitably cause gangrene or an automatic universal contraindication. It is important information for the surgeon's access decision.

Venous mapping

Map the cephalic and basilic veins and relevant communicating/deep veins through the proposed access region. Use a warm environment, appropriate dependent positioning or a tourniquet when indicated, and minimal probe pressure. Document whether measurements were taken with or without augmentation, because distension changes diameter. A cold or compressed vein can appear falsely small.

Assess compressibility, continuity, wall thickness, intraluminal material, branches, depth from skin, and the available straight segment for cannulation. Follow the vein through the arm rather than measuring only favorable spots. A short large segment with a small scarred segment upstream may not provide a usable conduit. Mark significant variants and changes in caliber accurately for the surgical team.

Evaluate accessible axillary, subclavian, and internal jugular pathways with direct imaging and waveform comparison. Central segments can be inaccessible behind bone. A normal peripheral waveform does not prove that every central segment is normal. State limitations and communicate concern so that other imaging can be considered when needed.

Postoperative maturation

After fistula creation, the vein should remodel to carry adequate flow and permit safe repeated cannulation. Evaluate the feeding artery, anastomosis, outflow vein, depth, straight usable length, branches, and any stenosis or collection. Consider the clinical examination and dialysis requirements, not just a diameter and a calendar date.

The historical “Rule of 6s” describes commonly taught benchmarks near six weeks: flow around 600 mL/min, diameter around 6 mm, and depth no more than about 6 mm. It is a heuristic, not a guarantee of successful cannulation or a mandatory current KDOQI definition. KDOQI explicitly discusses limitations of the rule. Usable length, location, flow, depth, patient factors, and the cannulation team's assessment all matter.

Worked maturation case

At six weeks, a fistula has flow 650 mL/min, diameter 6.5 mm, depth 4.5 mm, and a straight segment 7 cm long. These findings meet the classic size/flow/depth heuristic and appear favorable. They do not independently authorize cannulation. The access team still evaluates healing, physical examination, safe needle placement, and the required dialysis performance.

In another case, flow is high but most of the vein is too deep to reach safely. Calling it “mature because flow exceeds 600” misses the practical problem. Document the depth and usable segment so the team can consider observation, superficialization, or another plan.

Communicate a usable map

The report should identify the side and intended region, measurement conditions, vessel diameters and depths at named sites, patency, relevant branches, anatomic variants, possible inflow/outflow disease, and technical limitations. Distinguish observed anatomy from a recommendation outside your scope. The purpose is to supply reliable information for an individualized access decision, not to force every patient through a fixed list of operations.

KDOQI vascular access guideline, 2019 update — checked October 18, 2026; see statements 7.5 and the maturation discussion.