Fistula

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"arteriovenous fistula" AND classification

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Arteriovenous (AV) Fistula - Definition, Types & Classification

Definition

An arteriovenous fistula (AVF) is an abnormal direct communication between an artery and a vein, bypassing the capillary bed. Blood shunts from the high-pressure arterial side to the low-pressure venous side, producing both structural and physiological consequences.

Harrison's Principles of Internal Medicine 22e, p. 2220
Bailey and Love's Short Practice of Surgery 28e, p. 1045

Pathophysiological Consequences

Effect	Mechanism
Venous arterialization	Veins become dilated, tortuous, and thick-walled due to high-pressure arterial blood
Increased cardiac output	Large fistulas create a significant left-to-right shunt
High-output cardiac failure	Consequence of sustained large-volume shunting
Venous hypertension	Peripheral edema, varicose veins, stasis pigmentation
Distal ischemia	"Steal" phenomenon - reduced arterial perfusion distal to the fistula

Classification

1. By Etiology

A. Congenital AVF

Result of persistent embryonic vessels that fail to differentiate into arteries and veins
Often multiple and extensive communications
May be associated with birthmarks (port-wine stains, cutaneous hemangiomas)
Can occur in almost any organ; frequently in the extremities
Difficult to treat because new communications develop after ligation

B. Acquired AVF

Two major subtypes:

i. Iatrogenic / Surgically Created

Created deliberately for hemodialysis vascular access (radiocephalic, brachiocephalic, brachiobasilic)
Also occur as complications of arterial catheterization (incidence: 0.2-2% post-catheterization femoral AVF)
Risk factors for iatrogenic femoral AVF: female sex, hypertension, ongoing anticoagulation, left-sided groin puncture, high-dose periprocedural heparin (>12,500 units)
Iatrogenic AVFs may close spontaneously in 38-56% of cases; traumatic ones rarely do

ii. Traumatic

Penetrating trauma: gunshot wounds, stab wounds
Surgical dissection injury
Rupture of an arterial aneurysm into an adjacent vein (uncommon)

2. By Location / Anatomical Site

Location	Examples / Notes
Peripheral / Extremities	Most common; femoral, radial, brachial AVFs
Pulmonary	Pulmonary AVF - often congenital, associated with hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu)
Renal	Renal AVF - congenital or post-trauma/biopsy
Splanchnic / Hepatic	Splenic AVF - cause of presinusoidal portal hypertension
Coronary	Coronary arteriovenous fistula - anomalous coronary origin draining into cardiac chambers
Carotid-cavernous	Carotid-cavernous fistula (CCF) - often post-traumatic; classified by Barrow's classification
Spinal/Dural	Spinal dural AVF - most common spinal vascular malformation

3. Surgically Created AVF for Hemodialysis Access (by anastomosis site)

These are the "gold standard" for long-term dialysis access:

Type	Artery	Vein	Notes
Radiocephalic (Brescia-Cimino)	Radial artery	Cephalic vein (wrist)	First choice; distal forearm
Brachiocephalic	Brachial artery	Cephalic vein (elbow)	Second choice
Brachiobasilic	Brachial artery	Basilic vein	Requires transposition; used when cephalic vein unavailable

Fischer's Mastery of Surgery 8e, p. 6991-6992

4. By Anastomosis Configuration

Type	Description
End-to-side	End of vein anastomosed to side of artery (most common)
Side-to-side	Side of vein to side of artery
End-to-end	End of vein to end of artery

Key Clinical Signs

Pulsatile swelling (if superficial)
Continuous "machinery" bruit - heard throughout systole and diastole
Palpable thrill over the fistula
Nicoladoni-Branham sign - reflex bradycardia on manual compression of the fistula
Skin warmth directly over the lesion
Compression of the proximal artery causes the thrill and bruit to cease

Diagnostic Workup

Duplex ultrasonography (DUS): First-line; shows high arterial peak systolic velocity proximal to fistula, pulsatile venous flow, turbulence at the fistula site, and rapid venous filling
CT angiography (CTA): Defines anatomy
Conventional angiography: Gold standard for mapping; guides endovascular treatment

Summary Table

Feature	Congenital AVF	Acquired Traumatic AVF	Surgical AVF (Dialysis)
Cause	Failed embryonic differentiation	Penetrating trauma, iatrogenic	Deliberately created
Multiplicity	Often multiple	Usually single	Single
Spontaneous closure	No	Rarely (iatrogenic: 38-56%)	N/A
Treatment	Conservative + embolization	Surgery/endovascular	Maintained as access

Sources:

Bailey and Love's Short Practice of Surgery 28e, p. 1045
Harrison's Principles of Internal Medicine 22e, p. 2220
Current Surgical Therapy 14e, p. 1150
Fischer's Mastery of Surgery 8e, pp. 6991-6992

Explain in diagram representation form

Generating Image

Medical educational diagram of Arteriovenous (AV) Fistula - Definition, Types and Classification. Clean white background, professional medical illustration style with color coding. Layout: Vertical flowchart/mind map with sections: 1. TOP CENTER - Title box: "ARTERIOVENOUS FISTULA (AVF)" with subtitle "Abnormal direct communication between artery and vein, bypassing the capillary bed" 2. ANATOMY DIAGRAM (center-left) - Simple cross-section showing: - Red arrow labeled "ARTERY (High pressure)" - Blue arrow labeled "VEIN (Low pressure)" - Green curved arrow between them labeled "AVF = Direct Shunt (bypasses capillaries)" - Small branching capillary bed shown separately as "Normal" and crossed out 3. CLASSIFICATION TREE (right side, branching): BRANCH A: "BY ETIOLOGY" → Congenital: "Failed embryonic vessel differentiation; Multiple communications; Associated with birthmarks" → Acquired: → Traumatic: "Gunshot/stab wounds; Surgical dissection; Aneurysm rupture into vein" → Iatrogenic: "Post-catheterization (0.2-2%); Surgically created for hemodialysis" BRANCH B: "BY LOCATION" → Peripheral/Extremities (most common) → Pulmonary (HHT) → Renal → Coronary → Carotid-Cavernous → Splanchnic/Hepatic BRANCH C: "DIALYSIS AVF TYPES" (table) → Radiocephalic: Radial art. + Cephalic vein (1st choice) → Brachiocephalic: Brachial art. + Cephalic vein (2nd choice) → Brachiobasilic: Brachial art. + Basilic vein (needs transposition) 4. BOTTOM ROW - "CONSEQUENCES" boxes: - Venous arterialization (dilated, tortuous veins) - Increased cardiac output → High-output heart failure - Distal ischemia (steal phenomenon) - Venous hypertension (edema, varicosities) 5. CLINICAL SIGNS box (bottom right): - Continuous machinery bruit - Palpable thrill - Pulsatile swelling - Nicoladoni-Branham sign (bradycardia on compression) Color scheme: Red for arterial, Blue for venous, Green for fistula connections, Orange for consequences, Purple for clinical signs. Bold headers, clean lines, arrows connecting sections.

Here is the full diagram covering all key aspects of AV Fistula:

What it shows:

Core concept - The direct artery-to-vein shunt bypassing the capillary bed
Classification by Etiology - Congenital vs. Acquired (Traumatic vs. Iatrogenic)
Classification by Location - Peripheral, Pulmonary, Renal, Coronary, Carotid-Cavernous, Splanchnic
Dialysis AVF types - Radiocephalic (1st choice) → Brachiocephalic (2nd) → Brachiobasilic (needs transposition)
Hemodynamic consequences - High-output failure, venous arterialization, distal steal ischemia, venous hypertension
Clinical signs - Machinery bruit, thrill, pulsatile swelling, Nicoladoni-Branham sign

Would you like a deeper diagram on any specific section - such as the dialysis fistula anatomy, or the hemodynamic changes in detail?

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