The Arteriovenous Fistula

The contract between this chapter and the reader.

1. 1. Apply an individualized access Life-Plan rather than a one-size rule.
2. 2. Rank the access types by outcome and justify the fistula-first preference.
3. 3. Preserve veins early to protect future access.
4. 4. Interpret pre-operative duplex vein and artery mapping.
5. 5. Choose the fistula location, starting as distal as feasible.
6. 6. Assess fistula maturation using the rule of 6s.
7. 7. Examine a fistula by inspection, palpation, and auscultation.
8. 8. Recognise and manage maturation failure.
9. 9. Decide when a graft or catheter is the better individualized choice.

A sixty-second reading. Each bullet stands alone.

• Access planning is an individualized Life-Plan across the patient's dialysis lifetime, not a single rule.
• By outcome, an arteriovenous fistula is preferred over a graft, and both over a tunneled catheter.
• Catheters carry the highest infection, thrombosis, and mortality risk, so they are minimized.
• Preserve veins early: avoid forearm venipuncture, PICC lines, and subclavian catheters, which cause central stenosis.
• Pre-operative duplex maps vein and artery diameter, patency, and depth before any fistula is created.
• Create the fistula as distal as feasible — radiocephalic first — to preserve proximal sites for the future.
• A fistula must mature: the vein arterializes over about six weeks or more before it can be cannulated.
• The rule of 6s: by about six weeks, flow ≥ 600 mL/min, diameter ≥ 6 mm, depth ≤ 6 mm.
• Examine every fistula — inspect, palpate the thrill, auscultate the bruit — and use arm-elevation and augmentation tests.
• Maturation failure is often a juxta-anastomotic stenosis or accessory veins, and is frequently salvageable by angioplasty or revision.
• Do not cannulate before maturation; rotate sites (rope-ladder) and avoid area puncture to protect the vessel.
• In a frail patient with limited prognosis or no time to mature a fistula, a graft or catheter may be the better individualized choice.

The medical core. An expert should agree access planning and the fistula are fully covered here.

Why it matters at the bedside

Dialysis is only as good as its access, and the best access is decided long before the first needle. Plan it early, protect the veins, build the fistula in the right place, and let it mature — and the patient gets years of reliable dialysis. Get it wrong, and they live on catheters and their complications.

The access Life-Plan and the hierarchy

• Access is planned as an individualized Life-Plan across the whole dialysis lifetime — anticipating future access needs and preserving options — rather than applying one rule to everyone. The guiding principle is the right access, for the right patient, at the right time.
• By outcome the hierarchy is clear: an arteriovenous fistula gives the best long-term patency and the lowest infection, a graft is next, and a tunneled catheter — carrying the highest infection, thrombosis, and mortality — is last and is minimized.

Preserving veins

• Future access depends on veins that have not been damaged. From early CKD, protect them: avoid forearm and antecubital venipuncture, peripherally inserted central catheters, and subclavian lines, which scar the central veins and can ruin an entire arm for access.

Pre-operative assessment and mapping

• Before creating a fistula, duplex ultrasound maps the vein and artery — their diameter, patency, continuity to the central veins, and depth — alongside a history and examination noting prior catheters, the dominant arm, cardiac status, and arterial disease.

Choosing the fistula location

• Create the most distal feasible fistula first — typically radiocephalic at the wrist — because it preserves the more proximal sites (brachiocephalic, brachiobasilic) for future access if the first one fails or wears out.

Maturation and the rule of 6s

• A new fistula must mature: under arterial pressure the vein dilates and its wall thickens until it can take repeated cannulation, a process of about six weeks or more. Maturation is judged by the rule of 6s — by roughly six weeks, a flow of at least 600 mL/min, a diameter of at least 6 mm, and a depth of no more than 6 mm.

Examining a fistula

• Every fistula is examined by look, feel, and listen: inspect for aneurysm and collaterals, palpate a soft continuous thrill at the anastomosis, and auscultate a low-pitched continuous bruit. The arm-elevation test (a normal fistula collapses) screens for outflow stenosis, and the augmentation test (the pulse strengthens on occlusion) screens inflow.

Cannulation

• Do not cannulate before the fistula is mature — early needling causes infiltration and damage. Once mature, rotate sites along the vessel (rope-ladder) rather than puncturing the same small area, which causes aneurysm and wall damage.

Maturation failure

• When a fistula fails to meet the rule of 6s, the usual culprits are a juxta-anastomotic stenosis or competing accessory veins. Duplex defines the problem, and many of these fistulae are salvaged by angioplasty, accessory-vein ligation, or surgical revision rather than abandoned.

When a graft or catheter is the better choice

• Fistula-first is a default, not a mandate. In a frail patient with limited life expectancy, poor vessels, or an imminent need for dialysis with no time to mature a fistula, a graft — usable sooner — or even a catheter by informed choice can be the better individualized decision. This is a genuine, values-informed choice, made with the patient.

Five fully-built tables.

Table A — The access hierarchy

Table B — Vessel preservation

Table C — Pre-operative mapping targets

Table D — The rule of 6s (maturation)

Table E — Examining a fistula

Visualise & Map

Numbered rules. These numbers are the cross-reference handle for the cases and flowcharts.

Clinical Reasoning

Five cases. Each stops you at a decision before it answers it.

Exhaustive. Every rule in the chapter is here.

Safety & Evidence

Panel A — Red flags

Panel B — NEVER DO

Anti-patterns clinicians fall into. Each becomes a Level 22 distractor.

The grade reflects strength of evidence, not importance.

Patient Decisions

Outcomes as natural frequencies. Figures are representative; the direction of effect is given where precise numbers are uncertain.

Decisions where the right answer depends on the patient's values and situation, not the evidence alone.

Effective-care decisions (not preference-sensitive)

• Preserving veins — the evidence and anatomy dictate it.
• Mapping before creation — standard of care.
• Choosing the most distal feasible site — to preserve proximal options.
• Not cannulating before maturation — safety dictates it.

The conversation rehearsed as a skill. Numbers trace to Level 14.

Apply & Test

Copy-paste chart notes that map to the real decisions in this chapter.

Template 1 — Access Life-Plan note

• Expected dialysis timeline: ___; dominant arm: ___; cardiac/arterial status: ___.
• Vein preservation in place (no PICC/subclavian/forearm draws): yes/no.
• Duplex mapping: vein ___ mm; artery ___ mm; continuity ___.
• Planned access and site: fistula (location ___) / graft / catheter; rationale ___.
• Shared decision recorded (if applicable): patient values ___.

Template 2 — Fistula maturation assessment

• Weeks since creation: ___.
• Rule of 6s: flow ___ mL/min; diameter ___ mm; depth ___ mm — mature? yes/no.
• Exam: thrill ___; bruit ___; arm-elevation ___; augmentation ___.
• If not mature: duplex finding ___ (juxta-anastomotic stenosis / accessory vein).
• Plan: cannulate / angioplasty / revision / reconsider access.

Pre-rounds compression. Rules only.

Active recall. At least one card per objective.

Micro-teaching for rounds. Two scenarios, five steps each.

Metacognition anchored to this chapter's tensions. No answers provided.

1. 1. “Fistula-first” is a good rule that becomes a bad one when applied to the wrong patient; how do you know which patient is in front of you?
2. 2. Vein preservation depends on colleagues who don't see the future access; how would you make that discipline stick across a whole team?
3. 3. When a frail patient chooses a catheter against the hierarchy, how do you respect that choice while being honest about its risks?
4. 4. How long do you persist trying to salvage a fistula before its failures cost the patient more than a different access would?
5. 5. The access decision is made once but lived with for years; how do you keep the Life-Plan a living document rather than a one-time form?

Nine items, each anchored in this chapter. At least one per objective.