Arteriovenous fistula

An arteriovenous fistula is a surgically created anastomosis between an artery and a vein. Its main use is to dilate a vein for easier access in patients requiring regular haemodialysis.

Examining an AV fistula

Look

• General inspection
  • Patient well/unwell
  • In pain
• Fistula
  • Type of fistula
    • Radiocephalic AV fistula (most): radial artery to cephalic vein at wrist
    • Brachiocephalic AV fistula = brachial artery to cephalic vein in antecubital fossa
    • Brachiobasilic transposition AV fistula = brachial artery to transposed basilic vein in upper arm
  • Scars
  • Signs of inflammation: rash, erythema, swelling
  • Arm elevation test (for outflow obstruction): fistula should collapse on arm elevation
• Veins              
  • Presence of collateral veins (suggest venous stenosis)
• Hands – compare to other side
  • Oedema
  • Signs of ischaemia (Steal syndrome = vascular insufficiency secondary to AV fistula)

Feel

• Thrill: a thrill is normal but it shouldn’t be pulsatile
• Consistency: should be soft and easily compressible
• Augmentation test (for anastomotic stenosis): occlude vein 1-2 cm above anastomosis. If arterial pressure is adequately conducted (i.e. there is no anastomotic stenosis), a pulsation in the vein will be seen. NB: if vein is pulsatile anyway, there is venous outflow stenosis.

Listen

• Bruit: should be a soft machinery–like rumbling sound (high-pitched = stenosis)

Questions and more details about arteriovenous fistulae

Why is a fistula needed?

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How long does it take for an AV fistula becomes patent?

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How is an AV fistula used?

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What are the complications of an AV fistula?

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What special instructions should be given to a patient with a new AV fistula?

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What are the advantages of an AV fistula over a central venous catheter?

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