Kidney transplantation is something everyone has heard of for human patients but haven’t really thought about for pets. It turns out that organ transplants are not very available for our pets; however, there is a notable exception and that is in kidney transplantation for cats.

To uninitiated, the impression may be that once one receives a new kidney, life is renewed and all one’s kidney problems are solved. In fact, this is hardly the case. There are immune suppressive medications needed to prevent rejection of the new organ and other considerations. A kidney transplant is a very big deal for a cat or a human. We will not be reviewing the human aspects of kidney transplants but will present the details to be considered when deciding on a new kidney for one’s pet.

WHERE DO THE DONORS COME FROM & WHAT HAPPENS TO THEM AFTER?

This is an important ethical question for everyone involved in the feline transplantation program. It is no one’s wish to harm the donor cat who cannot voluntarily become an organ donor in the way a human can nor is there a mechanism to harvest organs from comatose brain damaged patients as might be done for humans.

Feline kidney donors come from research facilities. These cats are classified as “specific pathogen free” which means they are free from infectious diseases. They are matched by blood typing to the recipient cat. A research cat is selected and a kidney removed for the recipient. After the procedure, the owner of the recipient cat must adopt the donor.

One enters the program with one cat and leaves with two cats.

For cats, the use of a related donor is not necessary.

IS YOUR CAT A CANDIDATE?

Kidney transplantation is not a procedure that is left until all medical therapies have been exhausted. The best candidate is free from other medical problems besides the kidney disease. Typical screening includes:

• Basic blood panel (including thyroid level) and urinalysis
   
• Urine culture (elimination of latent infection is crucial)
   
• Feline Leukemia Virus and Feline Immunodeficiency Virus screening
   
• Ultrasound examination of the heart (heart diseases that involve high blood pressure development can damage the new kidney)
   
• Screening for Toxoplasmosis (the immune suppressive drugs needed to maintain the new kidney could re-activate a latent infection with this parasite).
   
• Blood typing
   
• Teeth cleaning (performed under anesthesia)

Different programs may have additional required screening tests such as kidney biopsy, intestinal biopsy, test doses of immune suppressive medications etc. Obviously the details would be provided by the specific program you are considering.

If the cause of the kidney failures is felt to be something that would lead the new kidney to fail as well, this may disqualify the patient from the program. Such conditions would include: renal lymphomaLymphoma, amyloidosis (a malignant protein deposition), and pyelonephritis (a deep kidney infection though if the infection is truly felt to have been eliminated, the patient might still qualify).

Cats with relatively early kidney failure are not yet candidates for transplantation. Cats with advanced kidney failure are not good candidates either, though, through dialysis (available at advanced critical care facilities such as those that perform kidney transplants) the values may be improved. The best candidates are those with an acute cause of kidney failure (such as a poisoning), cats who do not respond well to the usual medical management, or cats with a creatinine >4.0 mg/dl. The cat should have a decent appetite and be as strong as possible prior to this very major surgery.  Again, each transplant center will have its own criteria.

Prior to surgery, the recipient cat should be made
as stable as possible. Usually a blood transfusion is needed
to correct the renal failure associated anemia.
Sometimes dialysis is needed.

WHAT KIND OF HOME CARE WILL THE RECIPIENT REQUIRE?

The recipient is going to require suppression of his or her immune system for the rest of his or her life. Medications begin a few days before therapy. The heart of this therapy is a medication called “Cyclosporine,” a medication which has revolutionized organ transplantation for humans. Prednisone, a commonly used cortisone derivative, is typically used as well at least to start.

Cyclosporine is typically given twice a day with the lowest blood level of the day being approximately 500 ng/ml around the time of surgery and lowering to 250 ng/ml after a month or so of recovery after surgery. (Rejection of the new kidney occurs when levels dip below 200 ng/ml).

Cyclosporine has some disadvantages which include:

• Expense (Concurrent administration of ketoconazole, a medication normally used to treat fungal infection, has an added benefit of “potentiating” cyclosporine. This means that less cyclosporine is needed to achieve the desired effect. As long as ketoconazole is well tolerated, a substantial financial savings can be realized.  Additionally, if ketoconazole is used, it becomes possible to dose the patient only once a day rather than twice.) Approximately 30% of transplant patients will not be able to utilize this protocol due to the development of excessive cyclosporine levels or liver enzyme elevations from the ketoconazole.
   
• Periodic blood level monitoring is needed to check that the right dosage is being used. (For most drugs “what you take is what you get.” For other drugs there are individual variations in how the medication is absorbed into one’s body and cyclosporine is such a medication. When two patients take the same amount of drug, they may not achieve the same serum levels; some individual fine tuning is needed.)
   
• Long term use of cyclosporine increases the risk for the development of cancer, specifically lymphoma. At the University of Wisconcisin Renal Transplant Center, a 14% incidence of malignant tumor development is reported for cats with post-transplant time (and thus cyclosporine use time) of greater than one year.

WHAT ARE POTENTIAL COMPLICATIONS TO THE RECIPIENT?

There are basically three main complications:

• Rejection of the new kidney (which can occur at any point after transplantation). When a kidney is rejected, the cat will go back into kidney failure and suffer all the toxic symptoms that accompany that diagnosis (nausea, malaise etc.) If therapy (i.e. more aggressive immune suppression) is initiated quickly, the kidney can be saved. Rejection can also be a more chronic and insidious process, gradually destroying the new kidney over years. This phenomenon is not well understood and it is not known how commonly this occurs.
   
• Infection from the immune-suppressive therapy.
   
• Stricture (narrow scarring) of the ureter which is the tiny tube that carries urine from the new kidney to the urinary bladder. If this occurs, another surgery is needed to trim the scarred area and re-attach the ureter to the urinary bladder.

WHAT KIND OF SURVIVAL TIME CAN YOU EXPECT?

In a recent study, 59% of renal transplant patients were still alive 6 months after surgery and 41%  were still alive 3 years after surgery. Apparently the first six months is a somewhat crucial time in determining long term survival.

The University of Wisconsin Renal Transplant Center reports 70% survival at 6 months and 50% survival at 3 years. Of cats that survived to be discharged from the hospital (i.e. they did not succumb to problems directly related to the surgery), 96% survived to 6 months.

Kidney transplantation is an expensive (several thousand dollars) undertaking. It involves the adoption of a donor cat and long term medication and blood testing for the recipient. If this is something that you are seriously considering, be sure to discuss the procedure with the transplant center most local to you as well as with your regular veterinarian.

The feline CRF information center has assembled a list of renal transplantation centers and contact information. To view this list visit:

http://www.felinecrf.com/transb.htm