Q Bailey is our 12-year-old Boykin Spaniel. He doesn’t look old and he has the spirit of a puppy. But he is declining because, according to our veterinarian, he is in kidney failure. I don’t want to be selfish, but if there is a reasonable way I can keep him healthy or restore his health I would pursue it. I have read that some institutions are performing kidney transplants on cats and dogs. Is this a reasonable option?

A: Unfortunately, at least in this profession, the definition of “reasonable” varies widely. For me (Dr. Henri Bianucci), a procedure doesn’t necessarily have to make a patient live longer, but they should live significantly better. There should be a limited duration to any discomfort created by the procedure and the chances of complications should be small.

For example, amputating a painful leg with bone cancer may not add one extra day to a patient’s survival, but it will alleviate all the pain. They can spend their remaining months in comfort. To me, this is a reasonable surgery.

You are correct that kidney transplants are being performed in dogs. However, I do not believe that kidney transplants in dogs pass the reasonable test. In a recent study, the median survival time was only 18 days. Half of these patients died within 15 days. But the outcomes varied widely — two dogs lived past five years and one dog lived past 11 years. Another study had the patients surviving an average of eight months after transplantation.

Why the variability? One factor might be that all of these patients are not at the same degree of kidney failure to begin with. When kidneys are transplanted, the original kidneys are left in place. If they are in better condition to begin with, then they will contribute more function from the start and, possibly, for a longer period of time. Even if the transplant ceases to function, they may still chug on for a time. Also, kidneys do not all continue to decline at the same rate, so the time that the original kidneys can continue to help out is variable.

The cost of this procedure is high, as is the risk. Two animals, the recipient and the donor, must undergo invasive procedures, and the owner must agree to adopt the donor dog. So when a veterinarian is going to perform this procedure, the patient has to be healthy enough to be considered a reasonable surgical risk. This means that most of them would not necessarily have died quickly had the procedure not been performed. In fact, many would likely have lived much longer had the procedure not been done and their kidneys managed conservatively.

In cats, the survival times are significantly better. In a study of 61 feline kidney transplants, 50 percent survived the first six months and 41 percent survived past three years.

The reason for the difference in dogs and cats appears to be that dogs’ immune systems mount a stronger rejection effort to these transplants. Therefore dogs must be treated much more aggressively with anti-rejection drugs, which significantly increase the risk of adverse side effects. Overall, this procedure could actually shorten survival times as it carries a high risk of complications, requires intensive management with potent drugs and puts two animals through surgery.

At this time, my opinion is that this is definitely not a reasonable option for dogs. Although the statistics are better in cats, it is still not clear to me that these patients are living longer or better overall.

Dr. Henri Bianucci and Dr. Perry Jameson are with Veterinary Specialty Care LLC. Send questions to petdocs@postandcourier.com.