01OverviewDefinition, clinical context and the essential points that orientate the chapter.
Stenosis develops through neointimal hyperplasia and remodelling at predictable stress points: the juxta-anastomotic segment and outflow vein in fistulas, the cephalic arch in brachiocephalic access, and central veins after catheter or device injury. Progressive resistance changes the physical examination and dialysis performance. Flow falls with inflow limitation, pressure rises upstream from outflow obstruction, cannulation becomes difficult and haemostasis takes longer. Severe lesions promote stasis and thrombosis, converting a planned problem into an access emergency.
UKKA recommends intervention only when radiologically significant stenosis accompanies clinical dysfunction. KDOQI likewise separates clinical monitoring from device-based surveillance and advises against pre-emptive angioplasty of a stenosis found without clinical indicators. Once thrombosis occurs, early declotting can preserve the circuit and avoid catheter exposure, but thrombus is usually the consequence rather than the whole diagnosis. Review previous pressure, flow, adequacy and cannulation trends, image the whole circuit, and correct the culprit lesion during the salvage episode where feasible.
Key points
- An abruptly absent thrill or bruit is a time-sensitive thrombosed access: stop repeated cannulation and obtain same-day dialysis and access-team review for salvage.
- Salvage must address both thrombus and the underlying culprit stenosis; thrombectomy without lesion treatment invites early re-occlusion.
- Treat stenosis when clinical dysfunction and a radiologically significant lesion agree; do not perform pre-emptive angioplasty for an incidental narrowing without clinical indicators.
- Clinical indicators include new cannulation difficulty, aspiration of clots, failure to achieve target blood flow, prolonged post-needle bleeding, falling adequacy, arm swelling and abnormal pulse, thrill or bruit.
- Endovascular and surgical thrombectomy are both valid; choose through lesion anatomy, local expertise, prior interventions, infection, future access options and patient preference.
- Balloon angioplasty is the usual initial treatment for non-complex clinically significant stenosis; UKKA allows high-pressure balloons when necessary.
- Covered stents have defined roles, especially graft-vein anastomotic stenosis, but placement must not jail veins needed for future access.
- Routine systemic anticoagulation does not replace mechanical salvage and exposes dialysis patients to substantial bleeding risk.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Neointimal hyperplasia
Endothelial injury, altered shear and proliferative remodelling narrow common stress points, especially juxta-anastomotic and outflow segments.
Repeated vessel injury
Cannulation trauma, prior catheters, devices and interventions promote scarring, central stenosis, aneurysmal change and disturbed access flow.
Systemic and dialysis factors
Hypotension, dehydration, compression, hypercoagulability and low cardiac output can precipitate thrombosis when circuit reserve is already limited.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Inflow restriction
Arterial or juxta-anastomotic narrowing reduces circuit flow, producing a weak pulse, short thrill and inability to sustain prescribed dialysis blood flow.
- 2Outflow resistance
Venous narrowing raises upstream pressure, causing pulsatility, collateral veins, prolonged needle-site bleeding, swelling and eventually stasis.
- 3Thrombotic occlusion
Critical flow reduction and disturbed shear permit clot to propagate through the access, abruptly abolishing the thrill and preventing dialysis.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
The access may have a weak pulse and discontinuous or short thrill, poor pulse augmentation, low achievable blood flow and repeated arterial-pressure alarms during dialysis.
A resistant pulsatile access, focal high-pitched systolic bruit, failure to collapse on arm elevation, arm swelling and prolonged needle-site bleeding suggest downstream resistance.
New difficult cannulation, aspiration of clots, unexplained adequacy decline, recirculation, rising venous pressures or falling access flow should be interpreted together and compared with that patient's baseline.
Sudden loss of the continuous thrill and bruit, a firm non-compressible segment and inability to aspirate blood are typical; pain may be modest, so absence of pain is not reassuring.
Fever, rigors, purulent drainage, erythema, fluctuance or exposed material accompanying thrombosis raises a different emergency because declotting may disseminate infection.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Immediate access and dialysis assessmentFirst step - Why
- Confirm thrill or bruit loss, examine the whole circuit and limb, check last successful dialysis, volume state and urgent biochemical need.
- Interpretation and limitations
- A silent access with urgent dialysis indication requires two parallel plans: access salvage and safe temporary dialysis delivery if salvage cannot occur in time.
- 02
Duplex ultrasound — preferred initial circuit imagingPreferred - Why
- Locate thrombus, quantify inflow and outflow, identify stenosis, aneurysm or collection, and assess adjacent arteries and veins without iodinated contrast.
- Interpretation and limitations
- A focal velocity and calibre change is interpreted with flow and clinical dysfunction; an isolated percentage narrowing without a matching clinical indicator is not automatically a treatment target.
- 03
Fistulography during planned intervention - Why
- Define the complete access circuit and permit angioplasty, thrombectomy or adjunctive treatment in the same session.
- Interpretation and limitations
- A culprit lesion generally narrows the lumen by at least half and matches the clinical pattern; technical angioplasty success aims for minimal residual stenosis and restored flow.
- 04
Blood cultures and infection work-up - Why
- Investigate fever, rigors, purulence, access tenderness or systemic illness before manipulating a potentially infected thrombus.
- Interpretation and limitations
- Positive cultures or deep access infection changes the balance from routine declotting toward antimicrobial treatment and surgical source control.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Needle or machine problem
Poor blood flow during one session may reflect needle position, line kinking or machine factors; the access examination and repeat setup separate these.
Systemic low flow
Hypotension or poor cardiac output can transiently reduce dialysis flow without a fixed lesion, but may also precipitate thrombosis in vulnerable access.
Central venous stenosis
Prominent chest collaterals and whole-arm swelling suggest central outflow obstruction, which duplex may not exclude and may require venography.
Access infection
Painful erythema, purulence, fever or rigors suggests infection with or without thrombosis and changes procedural safety and source-control priorities.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Emergency pathwayAbruptly thrombosed fistulaFirst stepUse for a previously functioning fistula with absent thrill or bruit, failed cannulation or confirmed acute thrombotic occlusion.+
- 1Stop repeated needling, establish last dialysis and biochemical urgency, examine for infection, limb ischaemia, swelling and bleeding, and alert the access team the same day.
- 2Arrange urgent duplex or direct procedural imaging and choose endovascular or surgical salvage according to anatomy, expertise, infection, prior treatment and the person's access plan.
- 3Remove thrombus and identify and treat the culprit stenosis; confirm restored thrill, hand perfusion and usable flow before relying on the circuit for dialysis.
- 4AlternativeProvide safe alternative dialysis access if metabolic or fluid urgency cannot wait, avoiding sites that compromise planned future access.
02Routine dysfunction pathwayClinical indicators without occlusionUse for new cannulation difficulty, abnormal examination, prolonged bleeding, falling adequacy, pressure alarms or arm swelling while flow persists.+
- 1Compare findings with the patient's baseline and exclude reversible dialysis factors such as hypotension, needle position or machine-line problems.
- 2ConfirmatoryArrange timely confirmatory circuit imaging; KDOQI considers assessment within less than two weeks reasonable, accelerated when deterioration is rapid.
- 3Treat the radiologically significant culprit lesion, usually by balloon angioplasty for non-complex stenosis, and verify that the original clinical indicator improves.
03Conservative pathwaySurveillance-only anatomical stenosisUse when imaging incidentally shows narrowing but examination, cannulation, delivered dialysis and haemostasis remain stable.+
- 1Do not label anatomy alone as clinical failure; document the measurement, location and absence of dysfunction indicators.
- 2Continue skilled clinical monitoring at each dialysis session and teach the patient to report change in thrill, swelling, bleeding or cannulation.
- 3ConfirmatoryEscalationEscalate to confirmatory evaluation and treatment if a matching clinical indicator develops rather than scheduling automatic pre-emptive angioplasty.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Access loss
Failed or delayed salvage may permanently consume a fistula and force catheter use while another access is planned and matures.
Inadequate dialysis
Progressive dysfunction reduces delivered clearance and acute thrombosis can cause missed treatment, hyperkalaemia, pulmonary oedema and uraemic complications.
Procedure-related injury
Thrombectomy and angioplasty can cause vessel rupture, embolisation, dissection, bleeding, haematoma, infection or new distal limb ischaemia.
Recurrent stenosis
Angioplasty treats the lesion but restenosis is common, creating repeated procedures and prompting reassessment of the overall access strategy.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- At each dialysis session record look-feel-listen findings, cannulation difficulty, aspiration of clot, achieved pump flow, pressure alarms and haemostasis time relative to the patient's baseline.
- Trend delivered dialysis adequacy and access flow where the unit uses it, but investigate a coherent clinical change rather than treating a surveillance number in isolation.
- After intervention, confirm thrill and hand perfusion immediately, then document whether cannulation, dialysis blood flow, pressures, adequacy and bleeding return toward baseline.
- Track lesion location, device used, residual stenosis, complications and interval to recurrence because repeated short-lived procedures may justify surgical revision or a new access plan.
- Reassess infection signs after thrombectomy, particularly when thrombus was painful or inflammatory, and review cultures promptly if they were obtained.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Examination localises lesions
Pulse augmentation with inflow occlusion and collapse on arm elevation help distinguish inflow from outflow disease and guide the scope of imaging.
Thrombosis has a cause
Most occluded circuits contain a haemodynamically important stenosis. Removing clot without correcting that lesion restores a lumen but not durable physiology.
Stents can consume options
Before placing a stent graft, check the access life-plan because extension across a venous confluence may exclude a future fistula or surgical revision.
Recurrent failure changes strategy
Repeated restenosis, rapid re-thrombosis, poor cannulation or high treatment burden should prompt multidisciplinary review of surgical revision, abandonment and succession access.
11Common pitfallsFrequent interpretation and management errors.
- 01
Waiting for the next dialysis session after abrupt thrill loss reduces salvage opportunity and may allow dangerous hyperkalaemia or fluid overload to develop.
- 02
Calling every 50% narrowing clinically significant leads to unnecessary procedures when there is no matching dysfunction indicator.
- 03
Declotting through suspected access infection risks bacteraemia and fails to provide adequate source control.
- 04
Starting anticoagulation reflexively after thrombosis ignores the mechanical lesion and may worsen post-needle or procedural bleeding.
- 05
Judging technical angioplasty success without checking dialysis performance and the original clinical indicator mistakes an image result for patient benefit.