DIALYSIS: IS IT FOR YOUR PET?

The kidney is normally a tremendous organizer of our small ions. It determines how much calcium to keep and how to dump. It controls our blood’s pH by controlling which acids and bases to keep and which to lose. It controls sodium, potassium, calcium, carbon dioxide, water balance, and more. The kidney filters unwanted toxic biochemicals and gets rid of them in just the right amount of water necessary to maintain hydration. In failure, however, everything is haywire. Toxins build up and the patient is sick. The state of toxicity that results is called “uremia” or “uremic poisoning.”

Most every animal hospital can provide diuresis: a therapy where extra fluid beyond what the patient can drink is provided thus giving the kidney its medium so that it can remove toxic waste. This works well in a large number of patients but there comes a time when even with plenty of fluids, the sick kidney simply cannot get the toxins out. For most patients this is the “end of the line.” In fact, diuresis may be another choice, though it is substantially more expensive than diuresis and dialysis centers for pets are still few and far between.

What is Dialysis?

While there is such as thing as “peritoneal dialysis,” most people are referring to “hemodialysis” when they talk about someone having to have dialysis treatment for kidney disease.  A solution, called the “dialysate” is mixed so as to favor the diffusion of toxins from the blood of the patient across a membrane (the “dialyzer membrane”) into the dialysate. The cleansed blood is then returned to the patient. The dialysis machine has a pump (just the body has a heart to pump) which forces the patient’s blood into the machine.

There are actually numerous conditions that will benefit from this type of blood “cleansing” besides kidney failure.  Electrolyte imbalances , heart failure, and many poisonings can also be treated via hemodialysis.

Why is this so long in coming to pets?

Part of the problem has been that dialysis machines are generally designed for human patients.  The amount of blood that goes through the machine is too large a blood loss for a veterinary patient to withstand. Smaller machines had to be designed for patients as small as 5 or 6 lb cats.  Further, a large blood vessel must be accessible. The intravenous catheters are huge and very long so as to support the appropriate speed of blood flow through the dialyzer. Such catheters are very difficult to place; surgery may be necessary to place them. A permanent IV port under the skin may be needed if treatments are to be on-going.

How often is dialysis performed on a patient?

The patient who depends on dialysis to relieve the symptoms of uremia must have dialysis three times a week on the average. One must be able to bring the pet to the dialysis center with this frequency. Kidney transplant patients, or course, only require dialysis until they are well enough for surgery. Patients with a stone obstructing a ureter (the tube connecting the kidney and bladder) will require dialysis until stable for surgery. Other patients may require therapy indefinitely.

Does dialysis reliably control uremic poisoning?

Many patients do not respond to dialysis. How a given patient will do in part depends on what caused the kidney failure in the first place (toxin vs. infection vs. metabolic causes).   Here are some statistics:

Out of 138 dogs that failed to respond to conventional therapy at the University of California: 40% responded to dialysis. Infectious causes (generally leptospirosis) tend to have a better prognosis.  As leptospirosis has re-emerged has a cause of canine kidney failure the response rate has improved to 50%.

A study in 2003 with cats requiring hemodialysis, the response rate was 56% (the best was prognosis for those with a ureter obstruction where over 70% survived).

At what point in the treatment of kidney disease is dialysis recommended?

If dialysis is being considered, it is best not to wait until conventional therapy has completely failed and the pet is on death’s door. Let your veterinarian know from the start that this is an option you are interested in so that your veterinarian can consult with the dialysis center on the best time to refer.

What are the complications and disadvantages?

A new world of complications (beyond those of conventionally managed kidney patients) is introduced to the renal patient on dialysis.

• Malnutrition and Nausea
  The toxin build-up in kidney failure causes nausea directly and appetite loss follows. Toxins further cause ulcers in the stomach and intestine which contribute even more to the loss of appetite.  Once the toxins are removed, the intestine heals quickly but appetite loss may persist. Making the nutrition issue worse is the fact that dialysis patient have an increased protein requirement and an increased Calorie requirement.  It is particularly important for the dialysis patient to get nutrients in one way or another. Feeding tubes or IV feeding may be necessary.
   
• Metabolic Bone Disease
  When the sick kidney does not properly excrete phosphorus, calcium is mobilized in a complicated hormonal reaction (see Hypercalcemia). Dialysis patients appear to be at higher risk for actual broken bones than are conventionally managed kidney patients.
   
• Carnitine Deficiency
  Carnitine is a nutrient that facilitates the transport of the body’s energy sources. Unfortunately, dialysis inherently depletes the patient of carnitine.  Carnitine deficiency results in heart disease, low red blood cell count, and muscle weakness. Supplementation is often necessary for dialysis patients if dialysis is going to be regularly performed for periods longer than one month.
   
• Taurine Deficiency
  Taurine is an amino acid of animal protein origin. As is carnitine, taurine is lost in the process of dialysis with deficiency resulting in heart disease and (in cats) blindness. This amino acid must be supplemented for long term dialysis patients.
   
• Problems with the Dialysis Catheter
  The presence of the catheter may induce formation of a blood clot at the catheter tip. This can interfere with the high blood flow rates necessary for proper dialysis.  When a clot occurs, a forceful flushing of the catheter may be adequate to dislodge it but if not, clot dissolving medications must be used and this becomes expensive and may lead to inability to clot.
   
• Infection from the Dialysis Catheter
  An infected dialysis catheter is bad news. The resulting blood infection can be lethal and, at best, requires months of antibiotic therapy. One should be aware of skin reddening or pus at the catheter site. The development of a fever is of great concern so the owner should become familiar with taking the pet’s temperature.

How much does dialysis cost?

In preparation for this article we contacted the San Diego dialysis center listed below. We were told that the initial set up with the catheter, first week of treatments, feeding tube placement etc. typically runs $2500-$3000. After this, each treatment costs $500 (the average patient requires 3 treatments per week).

Where are the dialysis centers for pets?

The following are animal dialysis centers. Where possible, we have included web links which include more details about the procedure.  We hope to add more centers as they open. If you are aware of an animal dialysis center not listed here please contact us so it can be included.

The Animal Medical Center
510 E. 62nd St.
New  York, N.Y. 10021
(212) 838-8100
http://www.amcny.org/department/hemodialysis.htm

 

Tufts Foster Hospital for Small Animals
200 Westboro Road
North Grafton, MA 01536
(508-839-5302)

 

University of California Veterinary Medical Teaching Hospital
     Companion Animal Hemodialysis Unit
1 Garrod Dr.
Davis, CA 95616
(530-752-1393

 

University of California Veterinary Medical Center at San Diego
     Renal Medicine / Hemodialysis Service
6525 Calle de Nido
Rancho Santa Fe, CA 92067
(858) 759-7235

 

Veterinary Hospital of the University of Pennsylvania Hemodialysis Center
Matthew J. Ryan Veterinary Hospital
3900 Delancey St.
University of Pennsylvania
Philadelphia, PA 19104
(215) 898-4680