A dialysis fistula or dialysis shunt is a surgical ‘bypass’ (shunt) between an artery and a vein. In other words: an arteriovenous connection. The dialysis fistula is created in patients who need to be regularly attached to a dialysis machine due to terminal kidney failure (kidney insufficiency).
The dialysis machine carries out the blood cleaning function of the kidneys. It removes all the substances from the blood that would normally be filtered out by a healthy kidney and excreted from the body in the urine. The dialysis fistula is used to transport blood into the dialysis machine, where it is mechanically cleaned and then returned to the body. This procedure, called [haemodialysis], requires sufficient blood flow. Puncturing a vein is not enough to ensure sufficient blood flow, so it is necessary to increase the blood flow by connecting a vein with an artery. Once a dialysis fistula has been created, it can be punctured again later using a cannula whenever dialysis is required.
The dialysis fistula is usually created in the patient’s lower arm and is also known as a Cimino fistula. It was named after the vascular surgeon James Cimino who developed the technique in 1966.
What preparations are carried out before the procedure?
Prior to the operation, the blood vessels in the lower arm are examined using ultrasound and x-ray imaging (angiography). A contrast agent is injected for the angiography procedure. All blood-thinning medication must be discontinued prior to surgery.
How is the operation performed?
The Cimino fistula is usually created by connecting the radial artery and the cephalic vein in the patient’s lower arm. The operation is carried out with a local anaesthetic to numb the nerves in the arm. An incision is made to expose the artery and the vein. Then the vessels are temporarily pinched off, so that they can be opened and joined together. Once this is completed, the blood flow is restored and the incision is closed using one stitch. This is an outpatient procedure that takes around half an hour.
What is the success rate of this procedure?
This operation generally results in the successful creation of a dialysis shunt. Sometimes the blood flow through the shunt is insufficient to perform dialysis, or a thrombus (blood clot) may form. In such cases, it is necessary to create a new dialysis fistula.
What are the possible complications and risks of this procedure?
Normally this procedure is completed without any complications. The repeated puncturing of the fistula for dialysis can lead to changes in the nearby blood vessels. The walls of the vessels may become weak, narrowed (stenosis) or develop a bulge (aneurysm).
The connection between the artery and the vein means that blood is essentially ‘stolen’ from the hand. Sometimes this reduced blood flow can lead to what is known as steal syndrome, which involves pain, numbness and cyanosis of the hand. The arteriovenous connection also causes an increased return flow of blood to the heart, so the heart needs to work harder. If the patient’s heart is already damaged in some way, this can lead to heart failure (cardiac insufficiency).
What happens after the operation?
After the operation, the shunt cannot be used for dialysis straight away. The vein must first become accustomed to the increased blood flow and pressure that results from the connection with the artery. This process usually takes four to six weeks. Once the dialysis shunt has formed, it can often be used for several years. It is very important that the patient monitors their shunt. A functioning shunt produces a rhythmic buzzing or vibration, which can easily be felt by touching the skin over the shunt. Any changes in the area around the shunt or the arm should be immediately checked out by a doctor.