THE DOG’S KIDNEY
THE COMPLETE PICTURE
The mechanism of the kidney is a wonderful organizer of the small ions in the body. It determines how much calcium to keep and how much to get rid of. 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 much more. The biggest function of the kidney is to filter unwanted toxic biochemicals and gets rid of them in just the right amount of water necessary to maintain hydration. In failure, however, everything malfunctions. The wrong things are dumped, the wrong things are kept, toxins build up and the patient is sick. The state of toxicity that results is called uremia or uremic poisoning.
Almost every animal hospital can provide diuresis, a therapy in which extra fluid beyond what the patient can drink is provided, thus giving the kidney a boost to remove toxic waste. This works well in a large number of patients but there comes a time when even with plenty of fluids, the damaged kidney just can’t get the toxins out. For most patients, this is the end of the line. But they may be another solution, dialysis, though it is substantially more expensive than diuresis and facilities that perform dialysis for pets are still few and far between.
DIALYSIS FOR YOUR DOG
A dog’s jugular vein is where the process of dialysis and the cleansing of the blood begins. This is done using a membrane called a dialyzer membrane and fluid called dialysate. The blood is separated from the dialysate by the dialyzer membrane. The dialysate fluid is formulated so that the toxins in the blood will be attracted across the dialyzer and into the dialysate fluid.
There are two types of dialysis: peritoneal dialysis and hemodialysis. When most people refer to someone needing dialysis, they mean hemodialysis. The patient is hooked up to the dialysis machine by an intravenous catheter and a pump forces the patient’s blood into the machine for cleansing. The detoxified blood is returned to the patient. Peritoneal dialysis is less high tech and uses the patient’s own abdomen as the dialyzer membrane. The belly is filled with dialysate fluid, toxins are attracted into the fluid over several hours and the fluid ( with its toxins ) is drained from the belly at the end of the procedure.
The intravenous catheters used in hemodialysis are very large and very long so as to support the appropriate speed of blood flow through the dialyzer.
The catheters are difficult to place and so surgery may be necessary to do so. A long-term IV port under the skin may be needed if treatments are to be ongoing. A single catheter may be in place for months.
The treatment lasts from 3 to 5 hours, sometimes longer, during which the patient must calmly sit on a table attached to the equipment. Treatments typically are performed three times a week either indefinitely ( as in chronic renal failure ) or until the kidney has healed ( as in acute renal failure ).
There are many conditions that will benefit from this type of blood cleansing besides kidney failure. Electrolyte imbalances, heart failure, and many poisonings can also be treated with hemodialysis.
WHY ISN’T THIS TREATMENT FOR DOGS BEING OFFERED MORE OFTEN?
A major problem with dialysis machines is that they are generally designed for human patients. The amount of blood that goes through the human dialysis machine is too large a blood loss for a veterinary patient to withstand, so smaller machines had to be built. A veterinary dialysis machine had to be designed for patients as small as a 5 or 6-pound cat. Furthermore, a dialysis center requires specifically trained staff and 24-hour staffing. It was and is difficult to get such facilities financed. This procedure is still expensive and requires a dedicated owner but a least it is now an option.
HOW FREQUENTLY DOES DIALYSIS NEED TO BE DONE?
A dog that depends on dialysis to relieve the symptoms of uremia must have dialysis three times a week on the average. The dog owner must be able to bring the pet to the dialysis center with this frequency and leave the pet for the several hours needed. Kidney transplant patients, of 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 they are stable for surgery. Dogs who have lost kidney function acutely from a poisoning, many times antifreeze, or infection ( usually leptospirosis ) typically require a month of therapy while their kidneys heal. Some other patients will require therapy indefinitely.
WILL DIALYSIS REALLY CONTROL UREMIC POISONING?
Not always will patients respond to dialysis. How a given patient will do in part depends on what caused the kidney failure in the beginning ( toxin vs. infection vs. metabolic causes ).
In a study by the University of California, out of 138 dogs that failed to respond to conventional therapy for kidney failure, 40% responded to dialysis. Infections causes ( generally leptospirosis ) tend to have a better prognosis. As leptospirosis has re-emerged as a common cause of canine acute kidney failure, the overall response rate for dogs receiving dialysis has improved to 50%.
In a study in 2003 of cats requiring hemodialysis, the response rate was 56%; the best prognosis for those with a ureter obstruction was over 70%.
WHEN’S THE RIGHT TIME FOR DIALYSIS FOR YOUR DOG?
Do you want to try dialysis for your dog then it’s 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 they can consult with the dialysis center on the best time to refer.
ARE THERE COMPLICATIONS AND DISADVANTAGES TO THIS PROCEDURE?
This procedure can open up a world of complications ( beyond those of conventionally-managed kidney patients ) is introduced to the kidney patient on dialysis.
THE SIDE EFFECTS OF KIDNEY DISEASE
When there is kidney disease a toxin buildup occurs that can cause nausea and appetite loss with the dog. Toxins further cause ulcers in the stomach and intestine that 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 patients 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 damaged kidney does not properly get rid of phosphorous, calcium is mobilized in a complicated hormonal reaction. Dialysis patients appear to be at higher risk for broken bones than are conventionally-managed kidney patients.
WHAT IS 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.
WHAT IS TAURINE DEFICIENCY?
Taurine is an amino acid of animal protein origin. As is the case with carnitine, taurine is lost in the process of dialysis. A taurine deficiency can result in heart disease and ( in cats ) blindness if it is allowed to permit. This amino acid must be supplemented for long-term dialysis patients.
THE PROBLEM WITH A DIALYSIS CATHETER
The dialysis catheter may create a blood clot at the catheter tip. This can interfere with the high blood flow rates necessary for proper dialysis. When a clot occurs, the forceful flushing of the catheter may be enough to move it. If not, clot-dissolving medications must be used and this becomes expensive and may lead to an inability to clot.
THE DANGER OF DIALYSIS CATHETER INFECTION
An infected dialysis catheter is bad news. The resulting blood infection can be lethal and, at best, requires months of antibiotic therapy. Be aware of reddening skin or pus at the catheter site. A fever is of great concern so become familiar with taking the pet’s temperature.
HOW MUCH IS DIALYSIS?
The following information was taken from the UC Davis-SanDiego Dialysis website in July 2016, so keep in mind each facility will have its own price structure:
For dogs requiring dialysis: Our standard dialysis estimate is $3500-$4000 for the first 2 – 3 treatments and $600 – $700 per treatment thereafter. ( This includes lab tests, dialysis catheter placement, feeding tube placement, anesthesia, oxygen, and transfusion if necessary ), not including hospitalization at the Veterinary Specialty Hospital. The first three treatments will span 3 – 5 days. Depending on the caliber and intensity of care required by a given patient, hospitalization costs will range from $300 – $1200/day. Detailed estimates are provided once a patient is assessed. Clients whose patients will be receiving dialysis will be required to leave a deposit of between $2000 – $3000 before treatment and will also be required to leave a deposit at Veterinary Specialty Hospital.
CONTINUAL RENAL REPLACEMENT THERAPY
Continual renal replacement therapy ( CRRT ) is another form of blood filtration similar to dialysis; in fact, which procedure is the best choice for the human patient is hotly debated in human medicine. While dialysis removes toxins built up over a previous couple of days over a 3 to 5 hour treatment period, CRRT involves continual removal over a 24 to 48 hour period that mimics the patient’s natural kidney function more closely. The idea here is to continually remove toxins until they are all gone if that is possible. Sometimes a couple of treatments are needed. And unlike dialysis, CRRT is not a regularly performed procedure.
The catheters are similar to the dialysis catheters but because the procedure requires being hooked up to the equipment for up to two days, sedation is generally required for this entire period, although this depends on the hospital.
Lower blood flow rates are used in CRRT when compared to hemodialysis, which makes for fewer blood pressure issues. Also, the dialysis complications that are seen over time ( carnitine deficiency, high dietary calorie requirement, catheter infection, and most of the other issues listed above ) are not problems with CRRT because CRRT is a one-time treatment ). Sedation may be necessary for CRRT, depending on the facility.
Centers performing CRRT include the following. ( Please let us know of any others and we will add them to the list ):
Animal Medical Center at Cooper City, Florida. 9410 Stirling Road, Cooper City, Florida 33024
School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803-8410, 225-578-9600
Therapies such as blood cleansing are still new to the veterinary field because their use is high maintenance and costly. As pet insurance becomes more popular expense becomes less of a deterrent so more facilities are likely to open up. At the present time, dialysis is chiefly used on a temporary basis for acute conditions but as treatment becomes more available and affordable more chronic patients are likely to come forward. If dialysis is something you want to consider, let your veterinarian know so that you can be directed to the appropriate specialist.
