The Difference Between the 3 Types of Dialysis Accesses

Not all kinds of dialysis accesses are created the same

Vascular accesses
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When the kidney disease patient's kidneys have failed beyond a certain point, renal replacement therapy with dialysis is required.  There are 2 different kinds of dialysis, broadly speaking:

  • Hemodialysis
  • Peritoneal Dialysis

While peritoneal dialysis is done using a catheter inserted into one's belly, hemodialysis (the far more common modality of dialysis in the United States) is done via a so-called "vascular access." In plain English, a vascular access is the way by which blood is drawn from your body to be channeled into a dialysis machine where it's cleaned off toxins and excessive fluid.  This "clean" blood is then returned to your body through this very vascular access.

The vascular access is the dialysis patient's lifeline.  Without an access, there is no way to perform dialysis for the kidney failure patient.  The average kidney failure patient with no kidney function is unlikely to live beyond a couple of weeks without dialysis.

Different Kinds of Vascular Accesses Available

There are 3 different kind of possible options when it comes to choosing a vascular access for a hemodialysis patient:

  1. Arterio-venous fistula
  2. Arterio-venous graft
  3. Venous catheter

Difference Between the 3 Types of Dialysis Accesses 

Let me start by explaining the basic structural differences between the above 3 options. You might know that 'arteries" are blood vessels that carry oxygenated blood from the heart to different organs. Arteries break down into "capillaries", which eventually come together to form what are called "veins." Veins are the blood vessels that carry blood from which oxygen has been consumed, back to the heart. 

As you might appreciate from the above summary, arteries and veins are not connected directly. So you have these small "streams" of capillaries emerging from the division of arteries, which coalesce to form veins.  Now imagine if a structure were to form a "bridge" between the artery and the vein directly (hence bypassing the capillaries). This bridge is referred to as either an arteriovenous fistula or an arteriovenous graft.  The term "arterio-venous" refers to blood flowing from the artery to the vein. If this "bridge" happens to be a piece of the body's own blood vessel, it is called an arteriovenous fistula.  However, if the bridge happens to be an artificial extrinsic material, it is referred to as an arteriovenous graft.

Finally, a venous catheter is basically like a peripheral intravenous line.  Except that it is a little bigger and inserted into one of the big "central" veins in the neck or the groin.  It hangs entirely in a vein.  No so-called "bridge" exists between an artery and the vein in this case.  However, the catheter does have multiple ports, one of which is used to draw blood from the person into a dialysis machine, and another one from which the clean blood flows from the dialysis machine back into the patient. 

Here is a good video that demonstrates how a graft is placed and how it works.