KIDNEY TRANSPLANTS IN PETS
Kidney transplantation is something everyone has heard of for human patients, but may not have considered possible for pets. In fact, while transplantations are confined to specialized facilities with experienced surgeons, successful kidney transplants in cats have been going on since the mid-1980's. Canine programs have been less successful but are also available in limited facilities.
Kidney being removed from donor for kidney transplant
To the 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, not to mention potential for infection and other issues. A kidney transplant is a very big deal regardless of the species of the recipient. 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 transplantation program. It is no one’s wish to harm the donor animal 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 usually 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 and possibly blood cross-matching to the recipient cat (no other tissue-typing is necessary). 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.
Some transplantation programs allow the owner of the recipient cat to provide the donor. Donors must be young adults, generally at least 10 pounds in size, be free of infectious diseases such as Feline Immunodeficiency Virus, Feline Leukemia Virus, and Toxoplasmosis, and must have excellent kidney function. Basic blood testing and urine cultures must be normal.
One enters the program with one cat and leaves with two cats.
For dogs, the owner of the recipient is generally responsible for finding the donor. The University of California transplant program has been on hold since 2007, but as an example, their former donor guidelines were these: the donor must be less than 6 years of age, of similar size as the recipient (and preferably of the same breed), and, if the donor is not related to the recipient, special tissue matching is needed. Screening tests for the canine donor are similar to those for the feline donor but also include heartworm testing.
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:
Different programs may have additional required screening tests such as kidney biopsy, intestinal biopsy to rule out Inflammatory Bowel Disease, test doses of immune-suppressive medications, etc. Obviously the details would be provided by the specific program being considered.
If the cause of the kidney failure 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 lymphoma or other cancer, 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). Again, each program will indicate what conditions might serve to automatically disqualify a recipient.
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, and/or cats with a creatinine >4.0 mg/dl and a BUN < 100 mg/dl. (Cats with higher toxin levels have an increased risk for brain edema so the kidney disease must be controlled well enough to bring these values into an acceptable range prior to transplant). Anemic cats (cats with low red blood cell counts) are commonly treated with erythropoietin prior to transplant and cross matched with blood donors in preparation for the big day. 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.
IS YOUR DOG A CANDIDATE?
Recipient screening is similar to that for the feline patient though, again, heartworm testing is needed. Blood clotting tests are also needed for dogs. Similar conditions will also rule a patient out as a candidate (no cancer, heart disease, amyloidosis, or inflammatory bowel disease.) The adrenal hormone excess known as Cushing’s Disease also precludes participation in the kidney transplant program.
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. This not only requires a substantial financial commitment for the medication but also the ability to give the cat oral medication at least twice a day for the rest of his or her life. 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:
In the dog, azathioprine, an agent of chemotherapy, is also regularly used for its immuno-suppressive properties. It is usually given every other day long-term. Medication costs for dogs can vary from $150 per month to $2000 per month depending on the size of the dog.
WHAT ARE POTENTIAL COMPLICATIONS TO THE RECIPIENT?
There are basically three main complications:
There is an additional problem for dogs that is worth mentioning and that is intestinal intussusception. Imagine a telescope. Unfolded, it is basically a cylinder but folded, one segment collapses inside an outer segment. Now imagine this happening to a piece of intestine. A life-threatening obstruction results. To prevent this, the canine kidney patient has a procedure called "enteroplication" in conjunction with the transplant. In this procedure, the intestines are tacked down with sutures into a formation that precludes any telescoping motions. This, along with proper pain medication post-surgically, seems to prevent intussusception..
WHAT KIND OF SURVIVAL TIME CAN YOU EXPECT?
In a recent study of feline kidney transplants, 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 for cats 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.
In the dog, the picture is not nearly as bright. The University of California at Davis program was seeing about a 40% success rate and canine kidney transplantation is still considered in the investigational stage as new techniques are used to provide adequate immune suppression without complications.
Kidney transplantation is an expensive undertaking. (The University of California at Davis program, for example, required an $11,000 deposit for cats and $13,000 for dogs. Their surgeon has since moved to private practice where expense is typically greater). Transplantation involves the adoption of a donor 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 for both dogs and cats including contact information. To view this list visit:
This page is also part of the Chronic Renal Failure Center.
Last updated: 9/6/2016