Dialysis is a medical procedure performed on a person when one or both their kidneys fail. When the kidneys are no longer able to perform their daily tasks, the doctors recommend the patient to start dialysis. With the help of dialysis, the blood in the body is washed and poisons, waste and extra water are removed. Dialysis is a replacement for the function of the kidneys until the time the patient finds a healthy donor for a kidney transplant. During this procedure, the blood from the body is removed and cleaned in the dialysis machine and then pumped back into the patient’s body in a continuous cycle. To remove, clean and return blood, large tubes are put into the patient’s blood vessels. For this procedure to be successful, the patient needs to have blood vessels that have a large amount of blood flowing through them.
In order to develop a tube naturally, an AV fistula is created before dialysis. Surgery is carried out at which time two different types of blood vessels – arteries and veins are joined together creating an A–V fistula. The arteries carry oxygen-rich blood from the heart to the other parts of the body and the veins carry the blood back to the heart. By doing this operation, a vein can be developed into a tube that can be used for dialysis. As normal veins don’t have enough blood flowing through them a fistula is performed. Once the surgery is done, the body goes through some changes resulting in fistula maturation. It leads to more blood flowing into the vein. Once the fistula completely matures, the blood flow increases from 30 – 40 ml/min to over 300 ml/min. This helps in making the vein thicker and able to tolerate the large dialysis needles.
The thing with fistula is, not all can be used during dialysis. Unfortunately, some of the fistulas get blocked very soon after the surgery while the open ones fail to mature. This could be due to many factors like smaller blood vessels that never enlarge enough for use, weak heart pump leading to weak blood flow into the veins, damaged blood vessels due to needles/samples turning into an unusable fistula and blocks in the arteries leading to less blood flow.
The majority of the fistulas are made in the arms by injecting an anaesthetic into the area of operation. As it’s a small procedure, the patient can be awake throughout the operation. Fistulas are performed on the arms and on rare occasions they are done on the legs.
There are different alternatives to a fistula but most of the times the preferred option recommended by the doctors is to use one’s own blood vessels. That being said, plastic tubes i.e. catheters is one of the options, but it carries a high risk of infection and blockage. The second option is the AV Graft. Here, if the patient doesn’t have suitable blood vessels, the doctor may tell them to use a plastic graft to be placed under the skin. Other options include Peritoneal Dialysis and Tunnelled catheters.
The most common areas to make fistulas are wrist and elbow. Whether if it’s possible completely depends on the suitability of the patient’s blood vessels. As all fistulas don’t work forever, the doctor after a thorough examination will preserve as many options as possible which will be suitable for the patient. As fistulas can be affected by disease or not function properly like other body parts, procedures like angioplasty can be performed to save them.
Doctors recommend the best time to make a fistula is before starting dialysis. Patients with deteriorating kidney functions are advised to get a working fistula ready well before dialysis is performed to avoid plastic tubes and their risks.
Dr. Robbie George | Chief of Vascular & Endovascular Surgery | Mazumdar Shaw Medical Center, Bommasandra, Bangalore