What is a kidney transplant?A kidney transplant is the operation by which a kidney is removed from one person (the donor) and implanted into another person (the recipient). The donor can be a brain-dead organ donor, a living related donor or sometimes even a living unrelated donor.
When is a kidney transplant necessary?
End-stage chronic renal failureThere are many different causes of chronic kidney failure. Whatever the cause of the kidney failure, you cannot survive without functioning kidneys. However, many people live perfectly well with kidneys that are functioning less than one hundred percent. Once kidney function deteriorates beyond a certain point, the loss of function tends to become progressive.
When your kidneys can no longer sustain you, this function can be performed by long-term dialysis. Many people on dialysis, although not all, are suitable candidates for a kidney transplant.
If both kidneys need to be removedSometimes an otherwise healthy person needs to have both kidneys removed. An example of when this would be necessary is severe trauma (injury) to both kidneys. Someone like this would be a good candidate for a transplant.
Most potential transplant recipients will be on a dialysis programme while they wait for a suitable kidney to become available. People on a transplant waiting list need to be prepared to come into hospital at short notice. The waiting list of a transplant programme is usually held in a central location which covers the whole country. Once a kidney becomes available for transplantation, a scoring system is used to determine the best recipient of that specific kidney.
Various systems are used but most include factors such as length of time on the waiting list, accuracy of the match between donor and recipient blood groups and tissue typing, and the relative ages of donor and recipient. If a kidney that is harvested (removed from a donor) in a certain region cannot be used within that region, then it will be offered to patients outside of that region.
Where do the kidneys for transplantation come from?
- Brain-dead organ donors (cadaver transplant)
- Living donors (related and unrelated)
Brain-dead organ donorsThe majority of organs used in transplant programmes throughout the world come from brain-dead organ donors. These are people who have suffered serious injury or other medical conditions that have left them with beating hearts but brains that are already completely dead. Their circulation and ventilation are maintained on life-support machines, but if these were to be switched off they would stop breathing and die.
There are very strict laws and rules regarding the certification of someone as brain-dead. The diagnosis of the brain-dead state has to be definite. The brain-dead potential organ donor may either be a known card-carrying organ donor, or the family may give consent for the harvesting of organs.
Once the decision to proceed with organ harvest has been made, the donor is taken to the operating theatre where the organs to be used are removed. Occasionally only the kidneys are removed, but sometimes it is possible to use the kidneys, heart, lungs, liver and corneas from the same donor. Thus one organ donor can save or improve the lives of several different people awaiting organ transplantation for a variety of problems.
Once the kidneys are removed, they are placed on ice in sterile bags containing a preserving fluid. Kidneys can be safely preserved for up to 24 hours in this way, and can be transported if necessary. However, prolonged time between harvest and implantation is associated with a worse prognosis. Each of the two kidneys from one donor will be implanted into separate recipients.
Living related and unrelated donorsIn the case of a living donor the situation is completely different. The donor is a completely healthy person who will give one of his or her kidneys to the recipient. The donor is usually but not necessarily a relative of the recipient. The procedure is carefully planned beforehand. Obviously, the person donating a kidney needs to have two normal kidneys to start off with.
The decision to donate a kidney is not minor: as with any surgery, there is a small but definite risk involved in the operation to remove the kidney. A person can expect to lead a perfectly normal life with one kidney, provided that nothing happens to that one remaining kidney.
Tissue, such as a kidney, cannot be transferred from one person to another at random. The transplanted tissue will usually be regarded as foreign by the recipient’s immune system and rejected. This immune response is largely controlled by a set of genes called the major histocompatibility complex (MHC). These genes encode for certain antigens, called HLA-antigens. Potential donors and recipients need to be matched according to blood grouping and specific HLA-antigens. A close match between donor and recipient significantly reduces the chance of rejection of the transplanted kidney.
Due to their common genetic makeup, blood relatives will have a much better chance of a close match than unrelated individuals. Identical twins have identical genes (DNA) and will match perfectly. Transplantation between identical twins is the one situation where rejection is not a problem at all. In fact, these are the only transplant patients who do not need any anti-rejection medication.
With living donor transplantation, there is no need to store the transplanted kidney on ice for any significant length of time. The two patients are usually under anaesthetic in adjacent operating theatres and once the kidney has been removed from the donor it is implanted into the recipient straight away.
How is a kidney transplant performed?
Removal of kidney from donorThe operation to remove the kidney from the living donor involves a fairly long incision in the region of the lowest rib. Either kidney can be used, but it is customary to remove the left because of a longer renal vein on that side.
A live-donor nephrectomy involves a fairly long (15cm) incision in the flank over the lowest rib. This is quite a painful incision because several muscles are cut in the process. The unavoidable movements of respiration add to the discomfort. Patients can expect to stay in hospital for 4 to 5 days. Recovery to full fitness takes about 4 to 6 weeks. Statistically the risk for these donors developing renal failure later in life has been shown to be no higher than that of the general population.
In certain leading transplant units in the USA and Europe, the donor kidney is removed by laparoscopic (keyhole) surgery, with markedly reduced levels of discomfort for the patient. These techniques are not yet available in transplant units in South Africa.
Implantation of kidney in recipientMany people quite understandably assume that a transplanted kidney directly replaces one of the recipient's own kidneys. This is actually not the case. The new kidney is implanted into the pelvis, near the bladder. The recipient’s own (native) kidneys are left in place.
With the recipient under general anaesthetic, an incision is made in the lower abdomen, usually on the right side. A space is formed outside the sac that contains the intestines. The main blood vessels to the lower limbs and the pelvic organs (iliac vessels) run through this space. The main artery and vein of the kidney are joined to the iliac artery and vein respectively. This provides the blood supply for the transplanted kidney.
The ureter (drainage tube) of the donor kidney is joined to the recipient bladder. A catheter is left in the bladder while the newly joined areas heal. You can expect to stay in hospital for 7-10 days. Full recovery takes approximately six weeks, depending on your underlying health.
How well does a kidney transplant work?Kidney transplantation is one of the true success stories of modern medicine. The concept of transferring organs between people is not a new one, and the surgical procedure of kidney transplantation itself is also relatively straightforward. However, it was only with increased understanding of the immunology of rejection and the development of effective anti-rejection medication that this operation became a viable option for people with end-stage renal failure.
Kidney transplants work well. The overall patient survival is 95% at one year and 90% at two years. The one-year graft survival is 80%. Graft survival means that the transplanted kidney is still in the recipient and working. The one-year graft survival for living related transplants is 90%. Results are better with living donor kidneys because the genetic match is usually better between relatives, and these kidneys do not need to spend any time in storage.
Quality of life with a well-functioning kidney transplant is vastly superior to that on lifelong dialysis. Transplant recipients are independent and feel much better than they did while on dialysis. Haemodialysis has the problem of trice-weekly trips to the dialysis machine at the hospital, and peritoneal dialysis has the complication of daily fluid exchanges into and out of the abdomen. (See alternatives.)
What are the complications of having a kidney transplant?The complications can be divided into early and late complications.
The early complications include acute rejection, thrombosis (blockage) of the blood vessels supplying the kidney, urinary leakage, collections of lymph fluid in the wound and wound infection.
Thrombosis of the blood vessels occurs in 1-3% of cases, leading to death of the transplanted kidney. If thrombosis occurs the transplanted kidney is usually removed. Urine leakage from the point at which the ureter is joined to the bladder occurs in up to 10% of cases, but can usually be corrected. This is usually achieved by placing an internal drainage tube across the new joint of the ureter to the bladder. These tubes, also called stents, can usually be placed with a telescope passed into the bladder. These stents are left in place until the leakage stops. Occasionally it may be necessary to operate and repair the leak surgically.
Rejection remains a major problem in organ transplantation. There are different types and degrees of early rejection. The transplanted kidney undergoing rejection does not function well and is often painful and tender. It is often possible to treat rejection successfully with increased dosages of immunosuppression, but sometimes the kidney needs to be removed.
The main long-term complications are related to the life-long immunosuppressive medication that has to be taken to prevent rejection. Most transplant units use a combination of prednisolone, azathioprine and cyclosporin-A.
Complications include increased risk of infection, and problems with the bone marrow caused by the drugs.
Patients whose immune systems are compromised are more likely to develop cancer than people of a similar age whose immune systems are unimpaired. These patients are predisposed to infections with cancer-causing viruses and the immunosuppressant drugs themselves may have a direct role in promoting tumours because they can cause cell changes. A large study looking at tumours that developed in renal transplant patients found skin cancer (39%) and lymphoma (12%) to be the two most common cancers. Less common cancers included Kaposi sarcoma (4%), carcinoma of the cervix (4%) and renal tumours (4%).
Are there any alternatives to a kidney transplant?
- Chronic ambulatory peritoneal dialysis (CAPD)
HaemodialysisA dialysis machine can be regarded as a ”kidney machine”, in that it performs vital functions that an injured or diseased kidney cannot. The functions of the kidneys are complex and dialysis machines are large, but are getting smaller all the time as the technology improves.
The functions of the dialysis machine are to remove excess fluid and waste products from the bloodstream. The patient is connected to the machine for four to eight hours, three times per week. Some people have their own machines and can do their dialysis at home. For most kidney patients in South Africa, however, dialysis means a trip to the hospital every few days.
People on dialysis do not feel well. The blood levels of waste products are reduced to levels compatible with survival, but are nowhere near normal. Severe electrolyte (salt and other minerals) and fluid changes take place during the dialysis process. Survival is about 80% at two years, which is comparable with kidney transplantation.
Chronic ambulatory peritoneal dialysis (CAPD)The peritoneal cavity is the space around the intestines. The very large surface area of the intestines creates an effective surface for the exchange of fluids and molecules. Peritoneal dialysis utilises this surface.
With CAPD, a patient has a permanent small tube implanted that runs from outside your body into the abdominal cavity. A very specific dialysis fluid is inserted via this tube. The composition of the fluid is adapted according to the patient's specific needs. The dialysis fluid draws waste products and excess water from the bloodstream. The fluid is left in the abdomen for several hours before it is drained out, containing the waste products. This process has to be performed daily, but can be performed in the patient's home. The main problem with CAPD is infection, so it is not suitable for people without access to clean running water in their homes.
Written by Dr Pieter J le Roux MBChB, FRCS(Eng), FRCSI, FCS(SA)Urol Consultant Urologist, Tygerberg Hospital and the University of Stellenbosch Medical School.