Kidney failure that is permanent is called chronic renal insufficiency. There are 6 stages to kidney failure,. When you get to stage 5, you are much closer to ending dialysis. Your kidney doctor (nephrologist) will decide with you when its time to start dialysis. When to start dialysis really depends on a constellation of your symptoms (shortness of breath, nausea and loss of appetite, leg swelling) as well as the lab work. In general, when you kidney function is heading down below 10-12%, you are getting close to needing dialysis.
There are two ways of dialyzing, namely hemodialysis (blood dialysis) and peritoneal dialysis (dialyzing with a catheter that is placed in your abdominal cavity). We are going to deal with hemodialysis today. In order to have hemodialysis, you have to have a way to take the “dirty” blood out, pass it through the kidney machine, and then put the “clean” blood back into your circulation. This can be achieved by wants called an arteriovenous graft (AVG) or an arteriovenous fistula (AVF). Simply defined, an AVG is where we put a prosthetic material to connect an artery to a vein, and an AVG is when we connect one of your veins directly to an artery. Essentially, we are creating a high flow conduit that can accessed for pulling blood out of the circulation, and retiring it after putting the blood through the kidney machine.
An AVF is the best way of creating a dialysis access. When we create an AVG, we don’t put any prosthetic material into your body. We connect a vein in your arm to an artery, and create a low resistance pathway for blood to flow. Remember arteries bring blood down to the hand and veins take blood back up. When we sew a vein onto an artery, part of the blood flow that is going down the artery goes immediately back up the vein. In time, the vein gets bigger, and develops a stronger thrill (a “buzzing” feeling or vibration that you feel when you put your fingers over that area due to the rapid flow of blood in an elastic vessel). Fistulas can be created in the forearm at the wrist or in the upper arm. We always perform a preoperative ultrasound evaluation of the veins to assess the ideal site for creating the AVF, and I usually repeat the ultrasound at the time of surgery to conform the preoperative evaluation. The surgery itself takes about an hour to perform as an outpatient, and is not particularly painful. Once you recover from the surgery discomfort, you can use your arm like normal, including weight lifting and exercising. The advantage of the fistula is that is tends to last longer without clotting, and has a very low risk of getting an infection. The downside of an AVF is that is takes 6-8 weeks to “mature” or get ready to use, and sometimes needs a revision because of narrowing in the fistula, or development of large side branches that steal blood from the main body of the fistula.
If your veins are small or scared up from previous blood draws or I.V’s we sometimes will use prosthetic material to create the connection between the artery and vein. The most commonly used prosthetic material is polytetrafluoroethelene (PTFE). In essence, we create a pathway for dialysis by tunneling the PTFE under the skin in a straight line o a loop to connect an artery that supplies blood to the vein that takes blood back. The surgical site has to heal for 2-3 weeks before it can the used. In this situation, blood is taken out of the PTFE on the “arterial side” and returned after passing through the dialysis machine on the “venous side”. The advantage of an AVG is that is can be used within 2-3 weeks. the disadvantage is that it tends to clot more often and may have to be declotted, and it has a higher risk for infection.
The reason your nephrologist refers you to us as vascular surgeons before you might need to start dialysis is so that we can create an AVF or AVG well ahead of time. If you don’t have an AVF or AVG ready to use, and you need to start dialysis, we have to place tunneled catheters that hang out of your skin to use for dialysis immediately. It has 2 openings or ports, one to pull blood out and put it into the kidney machine, and the other to return the cleaned blood back to the circulation. Remember, there is nothing hanging out of you with an AVG or AVF. Tunneled catheters are what we would like to avoid if at all possible. First of all, its a nuisance having a piece of plastic tubing having out of your chest area. you can’t shower properly, and it hangs up on your clothes, and can sometimes be accidentally pulled out. But the bigger concern is that it is a piece of plastic tubing that is tunneled under your skin that ultimately ends up inside one of the main veins that drains towards the heart. It is an invitation to getting an infection. If we place these tunneled catheters (sometimes called permacaths), we would like to remove them as soon as possible to avoid the potential complications. That why it is far better to have an AVF created way ahead of time, even if you don’t need dialysis for 6 months, so that it will be ready for you when you need to start hemodialysis.
One final word on hemodialysis. Typically, you need to go to the dialysis center 3 times a week for 4 hour sessions of dialysis. However, more and more patients are able now to get dialysis machines at home, and so home hemodialysis is becoming a good option. I will discuss peritoneal dialysis at a later time.