Arteriovenous Fistulas

Key points

• Arteriovenous fistula (AVF) is a surgically created direct connection between an artery and vein, providing vascular access for haemodialysis.
• Thrombosis may present with loss of the normal thrill/bruit and failure of adequate dialysis flow; urgent vascular-access assessment is required.
• Stenosis may cause reduced dialysis blood flow, abnormal venous pressures or other access dysfunction; it is commonly detected by surveillance/clinical changes rather than by 'acute limb pain' alone.
• Steal syndrome is distal hand/limb ischaemia caused by diversion of arterial blood through the AVF; symptoms include pain, coldness, numbness or tissue ischaemia.
• Infection and aneurysmal/pseudoaneurysmal change are recognised AVF complications; repeated cannulation and high pressures can contribute to aneurysmal change.
• High-flow AVFs can rarely contribute to high-output cardiac failure, particularly when access flow is very high or cardiac reserve is limited.
• MRCP discriminator: absent thrill/bruit → AVF thrombosis; high venous pressures/reduced dialysis flow → stenosis; cold painful hand distal to AVF → steal syndrome.
• High-flow fistula + heart failure/high-output state is an uncommon but important complication.