Examining and Cannulating the AVF and AVG

Bottom Line

The access is kept alive at the chair, not in the operating room.

• Examine, don’t just measure. KDOQI 2019 recommends regular physical examination of every AVF and AVG by a knowledgeable practitioner and treats device-based surveillance as supplementary. It does not recommend pre-emptive angioplasty of a stenosis that produces no clinical indicator ¹.
• Listen to the character of the thrill, not just its presence. A stenosis turns a low-pitched continuous bruit into a high-pitched, systolic-only one. Loss of both thrill and bruit is thrombosis until proven otherwise — an urgent call ¹.
• The “Rule of 6s” is historical. When the NIH Hemodialysis Fistula Maturation Study tested similar thresholds, the likelihood of maturation was only approximately 50% ^1,2. Readiness is a clinical judgment, and experienced nurses’ assessment predicted maturity in 80% ³.
• Rope ladder is the default. Buttonhole cannulation carried 2.6 times the access-related bloodstream infection risk in national CDC surveillance data ⁴; KDOQI limits it to special circumstances and never in a PTFE graft ¹.
• The first needles go to the best hands. Cannulating a new fistula within 14 days of creation was associated with a 2.1-fold risk of failure (observational) ⁵, and a single infiltration before the first successful two-needle cannulation with 56% lower odds of maturation ¹.

1. Examining the AVF and AVG: Look, Listen, Feel

Why the examination comes first

Most AV access failure is stenosis followed by thrombosis, and stenosis rarely hides from a trained examiner. In a prospective diagnostic study of 142 consecutive patients referred for AVF dysfunction, a physical examination recorded in a sealed envelope before angiography agreed with the angiogram in 89.4% for outflow stenosis (kappa 0.78) and 79.6% for inflow stenosis (kappa 0.55); sensitivity and specificity were 92% and 86% for outflow and 85% and 71% for inflow lesions ⁶. Salman and Beathard’s review makes the same point from practice: the examination is quick, cheap, teachable to every hemodialysis caregiver, and comparable in accuracy to instrument-based approaches ⁷.

One caution about that accuracy. Asif’s cohort was patients already referred for dysfunction — a population with a high prevalence of disease — so the positive predictive value will be lower when the same examination is applied to every asymptomatic patient on a Tuesday morning ⁶. The examination earns its keep through repetition and trend, not through a single perfect call.

KDOQI 2019 codifies the examination in three statements ¹:

• 13.1 and 13.2: “KDOQI recommends regular physical examination or check” of the AVF and of the AVG “by a knowledgeable and experienced health practitioner, to detect clinical indicators of flow dysfunction” (Conditional/Strong Recommendation, Moderate Quality of Evidence).
• 13.3: nephrology trainees and practitioners involved in hemodialysis care should be trained in the physical examination of the AV access (Expert Opinion).

The examination, step by step

Adapted from KDOQI 2019 Table 13.1 ¹. Two bedside maneuvers turn the examination into a localizing test ¹:

1. Arm elevation test (outflow). Raise the access arm above the heart. A healthy fistula vein collapses. Failure to collapse means the blood cannot get out — an outflow stenosis. Excessive collapse of a venous segment is also abnormal and usually reflects poor inflow.
2. Pulse augmentation test (inflow). Occlude the vein a few centimeters above the anastomosis with a fingertip and feel the pulse between the anastomosis and the finger. It should strengthen. Lack of augmentation points to an inflow (arterial or juxta-anastomotic) problem.

2. Is the New Fistula Ready? Maturation Assessment

KDOQI 2019 asks for a surgical check for complications within 2 weeks of creation and an assessment for maturation by 4–6 weeks, with referral for further investigation when the fistula is not maturing as expected (Statement 10.1, Expert Opinion) ¹. It notes that 20% to 60% of AVFs fail to mature for dialysis use ¹.

The “Rule of 6s” of the previous guideline era — flow of at least 600 mL/min, diameter of at least 6 mm, and depth no more than 6 mm, classically checked at 6 weeks — should now be taught as historical. KDOQI 2019 notes that when the NIH Hemodialysis Fistula Maturation (HFM) Study tested similar thresholds (flow 600 mL/min, diameter 6 mm, depth 2 mm), the likelihood of maturation success was only approximately 50%, and concluded that “the cannulation criteria needs to be revisited” ¹. In the underlying HFM analysis, flow, diameter, and depth each predicted clinical maturation only moderately (cross-validated area under the curve 0.69–0.79) ².

Older single-center data still help the bedside examiner. Robbin and colleagues found that a minimum vein diameter of at least 4 mm and flow of at least 500 mL/min predicted an adequate fistula in 95% (19 of 20), versus 33% when neither was met — and that experienced dialysis nurses’ clinical assessment predicted eventual maturity in 80% (24 of 30) ³. The nursing examination is not a lesser test.

HFM also set expectations. Among participants already on dialysis, AVF maturation was only 29% at 3 months, 67% at 6 months, and 76% at 12 months; median time to maturation was 115 days; more than one third needed an intervention before maturation; and 47.5% of matured fistulas required further intervention to stay open or treat complications ⁸. A fistula is a maintenance program, not a single event.

3. Monitoring Versus Surveillance: What the Trials Say

The vocabulary matters because the guideline treats the two differently ¹:

• Clinical monitoring is examination of the access to detect clinical signs of dysfunction (arm swelling, changes in thrill or bruit, prolonged bleeding), supplemented by routine dialysis measures such as recirculation or a falling urea reduction ratio or Kt/V. Dynamic venous pressure counts as monitoring.
• Surveillance is periodic device-based testing beyond the clinical examination: access blood flow (Qa) by ultrasound dilution, Doppler, or other methods; static venous pressure; imaging for stenosis.

Source: KDOQI 2019 ¹. The accompanying note is the practical rule: “monitoring of vascular access is primary, while surveillance findings are supplementary, and action should not be based solely on surveillance findings” ¹.

The trial evidence behind that position.

• Meta-analysis of 14 RCTs (1,390 participants, fistulas and grafts, 6–38 months). Pre-emptive correction of stenosis did not significantly reduce access loss (RR 0.81, 95% CI 0.65–1.02) but did reduce thrombosis (RR 0.79, 0.65–0.97). Effects were larger in fistulas than grafts. The authors concluded that pre-emptive correction “does not improve access longevity,” though it “may be promising in fistulas” ⁹. Absolute risk reductions are not derivable from the abstract.
• Fistula trials. Tessitore’s 5-year open-label RCT randomized 79 forearm AVFs with angiographically proven stenosis over 50% to pre-emptive repair versus intervention only on clinical criteria; pre-emptive repair reduced failure and improved access survival (P=0.050) ¹⁰. Aragoncillo’s multicenter RCT randomized 207 prevalent AVFs to quarterly Qa surveillance added to classic monitoring: thrombosis fell from 0.086 to 0.025 per patient-year (thrombosis-free patency HR 0.30, 95% CI 0.11–0.82), but primary patency did not differ (HR 0.98, 0.57–1.61) ¹¹. The absolute difference of 0.061 thromboses per patient-year means approximately 16 patient-years of quarterly surveillance to prevent one thrombosis.
• Graft trials did not show a patency benefit, which is why the AVG statement is a firmer “do not suggest” ^1,9.

Critical appraisal. Thrombosis and “patency” are intermediate outcomes; access loss, catheter days, and hospitalization were not improved in pooled analysis ⁹. Small, open-label trials dominate (n=79 and n=207), and the intervention cannot be blinded ^10,11. Control arms received clinical monitoring, the current standard, so the comparisons are fair to modern practice ^9,10,11.

4. Access Dysfunction: The Clinical Indicators That Must Be Reported

KDOQI 2019 Table 13.2 lists the clinical indicators that suggest a clinically significant lesion — one that produces these signs and narrows the vessel by more than 50% relative to adjacent normal vein. When monitoring suspects one, imaging in less than 2 weeks with prompt treatment of a culprit lesion is considered reasonable (Statements 15.1 and 15.3) ¹.

Source: KDOQI 2019 Table 13.2 ¹. Three indicators deserve their mechanism spelled out:

• Rising venous pressure. Dynamic venous pressure is a monitoring parameter ¹. A sustained rise at the same blood flow suggests resistance downstream of the venous needle, in the outflow or central veins. Trend it; one high reading after a difficult venous needle is noise.
• Recirculation. Access recirculation happens when the blood pump pulls more than the access delivers, so dialyzed blood re-enters the arterial needle. KDOQI counts it as meaningful only “when needle placement is correctly spaced and placed” — so check spacing and orientation before blaming the access ¹.
• Arm swelling. Early central venous stenosis presents as asymmetric hand and arm swelling, aching or heaviness, venous collaterals, or skin discoloration; late disease adds swelling of the face, neck, breast, or trunk, stasis ulcers, and even hoarseness or respiratory compromise (KDOQI Table 26.1). Asymptomatic central stenosis found incidentally should not be treated (Statement 26.1) ¹.

5. Cannulation

The first cannulation of a new AVF

Timing. Readiness is a clinical judgment, not a calendar date. The only consistent timing signal is at the extreme: in DOPPS (observational), cannulating a new fistula within 14 days of creation was associated with a 2.1-fold higher risk of subsequent fistula failure, while cannulation at 15–28 days did not differ from 43–84 days ⁵. A later facility-level DOPPS analysis found no increase in failure with earlier cannulation practice patterns (fistula RR 0.72 at under 4 weeks versus 1–2 months; P=0.08), with the authors warning that selection bias could not be excluded ¹². Median first cannulation ranged from 25 days in Japan to 98 days in the United States ⁵.

Who needles first. KDOQI considers it reasonable that skilled cannulators with established high success rates perform initial cannulations, with structured training and supervision before and during a new cannulator’s early attempts and regular competency updates (Statements 11.6 and 11.7) ¹. The stakes are measurable: a single infiltration injury before the first successful two-needle cannulation was associated with 56% lower odds of overall AVF maturation (cited in KDOQI Guideline 12) ¹. Ultrasound guidance by a trained operator is reasonable for a first or new fistula, a fistula with prior infiltration, or to confirm the direction of flow (Statement 12.2) ¹.

Needle gauge and blood-flow progression. KDOQI 2019 makes no specific recommendation on graduated needle sizes or blood-flow advancement; it asks that they be individualized ¹. The NKF KDOQI Vascular Access Implementation Tool offers a practical matching table, with the instruction to follow unit policy ¹³:

Each row assumes a pre-pump arterial pressure no more negative than approximately −250 mm Hg. This is implementation guidance, not graded evidence ¹³. The only outcome data on gauge are observational: in a cohort of 7,058 patients across nine countries, 16-gauge needles were associated with a higher hazard of access failure than 15-gauge (HR 1.21) after adjustment ¹⁴. That association says nothing about the first weeks of a new fistula, when smaller needles and lower flows are the norm.

Rope ladder, area, and buttonhole

• Rope ladder (step ladder): both needle sites rotate along the whole length of the access at every treatment.
• Area (general area) puncture: needles repeatedly placed within millimeters of prior sites. KDOQI calls this “poor technique” that “leads to AV access aneurysms and damage and should be avoided” ¹.
• Buttonhole (constant site): the same site, angle, and depth each time, so that a scar tunnel forms and is then accessed with blunt needles.

KDOQI 2019 statements ¹: rope ladder is the preferred technique for AVFs (11.2, Conditional, Moderate Quality); limit buttonhole “only to special circumstances given the associated increased risks of infection and related adverse consequences” (11.3, Expert Opinion); avoid buttonhole in synthetic PTFE grafts because of “one-siteitis” (11.4, Expert Opinion). Buttonhole may be acceptable for a fistula with only a short or small cannulation segment, an enlarging aneurysm, or failure of rope-ladder cannulation in self-cannulators such as home hemodialysis patients with excellent hygiene and technique (Table 11.1).

The honest synthesis: buttonhole can be done safely in tightly run programs ^18,19, but the average unit sees more S. aureus bacteremia without a survival benefit ^1,4,15. For a home hemodialysis patient who genuinely cannot rope-ladder, KDOQI notes the infection risk of buttonhole is similar to that of a well-cared-for catheter, so the real comparison may be buttonhole versus catheter, weighed inside the ESKD Life-Plan ¹.

Needle orientation and cannulation mechanics

• Venous needle: always points in the direction of blood flow, toward the heart ¹⁴.
• Arterial needle: may point antegrade or retrograde. A retrograde arterial needle with the bevel down was associated with an 18% higher risk of access failure than antegrade with the bevel up; the other combinations did not differ significantly ¹⁴.
• Area puncture was associated with a significantly higher risk of access failure than rope ladder or buttonhole in the same cohort ¹⁴.
• Patient-applied arm compression during cannulation was associated with better access survival than a tourniquet (HR 1.30 for tourniquet) or no pressure (HR 1.25) ¹⁴.
• Know the flow direction before needling, especially in grafts and complex fistulas ¹.

Infiltration: prevention and management

KDOQI cites mild infiltration injury in more than 50% of AVFs and major infiltration in 5% to 7% ¹. At a US academic center (observational), major fistula infiltration occurred at a 5.2% annual rate; risk rose with age and with a fistula under 6 months old (43.5% vs 20.5%; OR 2.98, 95% CI 1.61–5.54). Each major infiltration generated a mean of 2.4 tests, surgery visits, or interventions; 26% of infiltrated fistulas thrombosed; and median catheter dependence was prolonged by 97 days ²⁰.

KDOQI grades injury as minor (ice and rest for 1–2 days, recannulate at the next session, two-needle cannulation re-established within 7 days), major (more than 7 days of recovery), or severe (transfusion, an emergency department visit, hospitalization, or a procedure) ¹. Management at the chair (Statement 12.1) ¹:

1. Any size: ice for at least 10 minutes, and do not push the blood pump to its maximum.
2. Moderate: withdraw the needle and hold manual pressure over the infiltration site.
3. Significantly large: decide whether dialysis is needed today. If it is, cannulate proximal to the injury; if that is not possible, do not re-attempt at the injured area until manual pressure and ice have been applied for 30 minutes.
4. Hematoma: measure the swelling, confirm flow in the access proximal and distal to it, and check circulation to the hand.

Post-dialysis hemostasis

Apply direct pressure to the bleeding site, and take care not to occlude the access outflow distal to it, because doing so raises intra-access pressure toward arterial levels ¹. Pressure should stop the bleeding without stopping the thrill. Whether manual compression or mechanical clamps better protect patency is listed by KDOQI as an unanswered research question ¹. Report bleeding beyond the patient’s usual for three consecutive sessions, any bleeding needing a suture, and any large hematoma ¹.

AVG-specific points

• Timing. Grafts are typically first cannulated 2–4 weeks after placement; in DOPPS, cannulation under 2 weeks was not associated with more graft failure than 2–3 weeks (RR 0.84, P=0.11) ¹². Early-cannulation grafts follow the manufacturer’s instructions.
• Never buttonhole a PTFE graft — rotate sites along the whole graft (Statement 11.4) ¹.
• Examination differences. The normal graft thrill is strongest at the arterial anastomosis but felt over the whole graft; a “mushy” graft suggests low flow; a strong pulse or thrill at one point suggests stenosis, most often at the venous anastomosis ¹.
• Surveillance. KDOQI does not suggest routine AVG surveillance beyond clinical monitoring (Statement 13.5) ¹.
• Hemorrhage risk. Grafts accounted for 55% of fatal vascular access hemorrhages in a CDC-led case review ²¹.

Evidence Gaps

1. Surveillance in fistulas. Small open-label trials show fewer thromboses without better primary patency ^9,10,11. A pragmatic trial with patient-important endpoints, such as catheter days and access loss, is needed.
2. Readiness to cannulate. The Rule of 6s performs at roughly coin-flip accuracy ^1,2; validated, bedside-usable criteria do not exist.
3. Needle gauge, flow progression, needle direction, and clamps. Every data point is observational or expert opinion ^1,13,14, and KDOQI lists each as a research priority ¹.
4. Buttonhole in modern hygiene-bundle programs. One trial and one long-running center suggest buttonhole can be safe with rigorous protocols ^18,19; national data say the average unit cannot reproduce that ⁴.

At the Chair

References

Numbered for this page. Each reference was checked against its PubMed record or the primary document (guideline, FDA label, agency page) in September 2026.

1. Lok CE, Huber TS, Lee T, et al. KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update. Am J Kidney Dis. 2020;75(4 Suppl 2):S1–S164. PMID: 32778223
2. Robbin ML, Greene T, Allon M, et al. Prediction of arteriovenous fistula clinical maturation from postoperative ultrasound measurements: findings from the Hemodialysis Fistula Maturation Study. J Am Soc Nephrol. 2018;29(11):2735–2744. PMID: 30309898
3. Robbin ML, Chamberlain NE, Lockhart ME, et al. Hemodialysis arteriovenous fistula maturity: US evaluation. Radiology. 2002;225(1):59–64. PMID: 12354984
4. Lyman M, Nguyen DB, Shugart A, et al. Risk of vascular access infection associated with buttonhole cannulation of fistulas: data from the National Healthcare Safety Network. Am J Kidney Dis. 2020;76(1):82–89. PMID: 32151430
5. Rayner HC, Pisoni RL, Gillespie BW, et al. Creation, cannulation and survival of arteriovenous fistulae: data from the Dialysis Outcomes and Practice Patterns Study. Kidney Int. 2003;63(1):323–330. PMID: 12472799
6. Asif A, Leon C, Orozco-Vargas LC, et al. Accuracy of physical examination in the detection of arteriovenous fistula stenosis. Clin J Am Soc Nephrol. 2007;2(6):1191–1194. PMID: 17928468
7. Salman L, Beathard G. Interventional nephrology: physical examination as a tool for surveillance for the hemodialysis arteriovenous access. Clin J Am Soc Nephrol. 2013;8(7):1220–1227. PMID: 23824199
8. Huber TS, Berceli SA, Scali ST, et al. Arteriovenous fistula maturation, functional patency, and intervention rates. JAMA Surg. 2021;156(12):1111–1118. PMID: 34550312
9. Ravani P, Quinn RR, Oliver MJ, et al. Preemptive correction of arteriovenous access stenosis: a systematic review and meta-analysis of randomized controlled trials. Am J Kidney Dis. 2016;67(3):446–460. PMID: 26776537
10. Tessitore N, Lipari G, Poli A, et al. Can blood flow surveillance and pre-emptive repair of subclinical stenosis prolong the useful life of arteriovenous fistulae? A randomized controlled study. Nephrol Dial Transplant. 2004;19(9):2325–2333. PMID: 15280529
11. Aragoncillo I, Abad S, Caldés S, et al. Adding access blood flow surveillance reduces thrombosis and improves arteriovenous fistula patency: a randomized controlled trial. J Vasc Access. 2017;18(4):352–358. PMID: 28430315
12. Saran R, Dykstra DM, Pisoni RL, et al. Timing of first cannulation and vascular access failure in haemodialysis: an analysis of practice patterns at dialysis facilities in the DOPPS. Nephrol Dial Transplant. 2004;19(9):2334–2340. PMID: 15252160
13. National Kidney Foundation. KDOQI Vascular Access Implementation Tool 11b: Cannulation — How to Cannulate & Manage Complications (Tables 11.a–11.d). 2022.
14. Parisotto MT, Schoder VU, Miriunis C, et al. Cannulation technique influences arteriovenous fistula and graft survival. Kidney Int. 2014;86(4):790–797. PMID: 24717298
15. MacRae JM, Ahmed SB, Hemmelgarn BR; Alberta Kidney Disease Network. Arteriovenous fistula survival and needling technique: long-term results from a randomized buttonhole trial. Am J Kidney Dis. 2014;63(4):636–642. PMID: 24239019
16. Muir CA, Kotwal SS, Hawley CM, et al. Buttonhole cannulation and clinical outcomes in a home hemodialysis cohort and systematic review. Clin J Am Soc Nephrol. 2014;9(1):110–119. PMID: 24370768
17. Wong B, Muneer M, Wiebe N, et al. Buttonhole versus rope-ladder cannulation of arteriovenous fistulas for hemodialysis: a systematic review. Am J Kidney Dis. 2014;64(6):918–936. PMID: 25110302
18. Vaux E, King J, Lloyd S, et al. Effect of buttonhole cannulation with a polycarbonate PEG on in-center hemodialysis fistula outcomes: a randomized controlled trial. Am J Kidney Dis. 2013;62(1):81–88. PMID: 23473984
19. Labriola L, Crott R, Desmet C, et al. Infectious complications associated with buttonhole cannulation of native arteriovenous fistulas: a 22-year follow-up. Nephrol Dial Transplant. 2024;39(6):1000–1007. PMID: 37873684
20. Lee T, Barker J, Allon M. Needle infiltration of arteriovenous fistulae in hemodialysis: risk factors and consequences. Am J Kidney Dis. 2006;47(6):1020–1026. PMID: 16731297
21. Ellingson KD, Palekar RS, Lucero CA, et al. Vascular access hemorrhages contribute to deaths among hemodialysis patients. Kidney Int. 2012;82(6):686–692. PMID: 22695325

Also in the Maintenance Hemodialysis module

Part of the Maintenance Hemodialysis mastery module. Module index.

• M17a: Anemia: targets, ESAs, and hyporesponsiveness
• M17b: Anemia: iron, HIF-PH inhibitors, and transfusion
• M19: Catheter care, lock solutions, and bloodstream infection
• Module: Intradialytic hypotension and dialysate cooling
• Clinical Mastery: Vascular access selection in older patients starting hemodialysis (ACCESS HD)
• Clinical Mastery: Enterococcal endocarditis in hemodialysis patients