Editing Haemodialysis access (section)

=== Aetiology of access failure ===

* CVCs
** For tunnelled CVCs - failure usually results from thrombus or fibrin sheath formation
* '''Autogenous access'''
** '''Stenosis''' (secondary to intimal hyperplasia)
*** Arterial inflow stenosis - much less common cause of stenosis than venous outflow stenosis. Can similarly limit flow, but in this case both needles are distal to the stenosis. Common mechanism of failure of autogenous AV access, occasionally leading to complete collapse of the outflow vein during dialysis. Stenosis of the anastomosis is by far the most common location.
**** Juxta-anastomotic stenosis - occurs within the first 3-4cm of the AVF. More common in radiocephalic fistulas.
*** Stenosis of the autogenous access itself - in response to perturbed flow and repeated cannulation. Swing segment stenosis is more common in brachiobasilic fistulas.
*** Venous outflow stenosis - classic cause. More common in brachiocephalic fistulas.
**** Cephalic arch
**** Central vein stenosis
*** Arterial inflow stenosis
*** Intervention needs to happen before thrombosis occurs, as they may have limited patency after thrombectomy
** '''Thrombosis'''
*** Often associated with underlying compromise to endothelial surface, and there is therefore a high recurrence rate
*** Most commonly occurs as a result of venous outflow stenosis, but can also occur with pooling of blood in pseudoaneurysms or inadequate arterial inflow
* '''Prosthetic access'''
** Arterial inflow stenosis
** Venous outflow stenosis secondary to intimal hyperplasia at the venous anastomosis, secondary to turbulence (most common failure mode)
** Thrombosis
*** Occurs more frequently than in autogenous access
*** Flow rates less than 600-800mL/min predicts thrombosis in a prosthetic access