kidney failure in dogs dialysis

By Isabella Storyclaire

last updated September 17, 2024

Contributions sourced from

The kidney is a tremendous organizer of our small ions. It determines how much calcium to keep and how much to dump. It controls our blood's pH by controlling which acids and bases to keep and which to lose. It controls sodium, potassium, carbon dioxide, water balance, and more. The kidney filters unwanted toxic biochemicals and gets rid of them using a process called excretion. Not only are toxins removed, but they are removed using just the right amount of water so that hydration is maintained. In failure, however, everything goes haywire. 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, 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 sick kidney simply cannot get the toxins out. For most patients, this is the end of the line. In fact, however, dialysis may be another choice. It must be understood that dialysis is substantially more expensive than diuresis, and centers that provide dialysis for pets are still few and far between.

Dialysis catheter placed in a dog's jugular vein. Image Courtesy of ACCESS Specialty Animal Hospitals

What Is Dialysis?

Dialysis is a process that can be thought of as cleansing the blood of toxins. This is done using a membrane called a dialyzer membrane and a 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 membrane 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.

Image Courtesy of ACCESS Specialty Animal

Hemodialysis (Description and FAQ)

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 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 three to five 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 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 with hemodialysis.

WhyIsThisSoLonginComingtoPets?

Part of the problem has been that dialysis machines 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. The procedure is still expensive and requires a dedicated owner but at least it is now an option.

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 average. The pet 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. Patients who have lost kidney function acutely from poisoning, usually antifreeze, or infection (usually leptospirosis) typically require a month of therapy while their kidneys heal. Other patients may require therapy indefinitely.

Does Dialysis Reliably Control Uremic Poisoning?

Not all patients 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).

Out of 138 dogs who failed to respond to conventional therapy for kidney failure diuresis at the University of California, 40% responded to dialysis.Infectious 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 was for those with a ureter obstruction where over 70% survived.

At What Point in Treatment 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 kidney patient on dialysis.

Malnutrition and NauseaThe toxin build-up in kidney failure causes nausea, and appetite loss follows. 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 thefact 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 DiseaseWhen the sick kidney does not properly get rid of phosphorus, 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.

Carnitine DeficiencyCarnitine 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 DeficiencyTaurine is an amino acid of animal protein origin. As is the case with carnitine, taurine is lost in the process of dialysis. Taurine deficiency can result in heart disease and (in cats) blindness if it is allowed to persist. This amino acid must be supplemented for long-term dialysis patients.

Problems with the Dialysis CatheterThe 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, a 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 inability to clot.

Infection from the Dialysis CatheterAn 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.

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 the 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. Unlike dialysis, CRRT is not a regularly performed procedure.

The catheters are similar to the dialysis catheters, but because the procedure requires being hooked 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.

Blood cleansing therapies such as these are still new to the veterinary field because their use is high maintenance and costly. Aspet 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. Costs vary and will depend on your pet's health status, the number of treatments necessary, and the facility.

Your veterinarian can refer you to the closest facility, and The American Society of Veterinary Nephrology and Urology (specializing in the kidneys and the larger urinary system) offers a list of facilities in North America.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.

End-stage renal disease

Overview

End-stage renal disease, also called end-stage kidney disease or kidney failure, occurs when chronic kidney disease the gradual loss of kidney function reaches an advanced state. In end-stage renal disease, your kidneys no longer work as they should to meet your body's needs.

Your kidneys filter wastes and excess fluids from your blood, which are then excreted in your urine. When your kidneys lose their filtering abilities, dangerous levels of fluid, electrolytes and wastes can build up in your body.

With end-stage renal disease, you need dialysis or a kidney transplant to stay alive. But you can also choose to opt for conservative care to manage your symptoms aiming for the best quality of life during your remaining time.

One of the important jobs of the kidneys is to clean the blood. As blood moves through the body, it picks up extra fluid, chemicals and waste. The kidneys separate this material from the blood. It's carried out of the body in urine. If the kidneys are unable to do this and the condition is untreated, serious health problems result, with eventual loss of life.

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Symptoms

Early in chronic kidney disease, you might have no signs or symptoms. As chronic kidney disease progresses to end-stage renal disease, signs and symptoms might include:

Nausea
Vomiting
Loss of appetite
Fatigue and weakness
Changes in how much you urinate
Chest pain, if fluid builds up around the lining of the heart
Shortness of breath, if fluid builds up in the lungs
Swelling of feet and ankles
High blood pressure (hypertension) that's difficult to control
Headaches
Difficulty sleeping
Decreased mental sharpness
Muscle twitches and cramps
Persistent itching
Metallic taste

Signs and symptoms of kidney disease are often nonspecific, meaning they can also be caused by other illnesses. Because your kidneys can make up for lost function, signs and symptoms might not appear until irreversible damage has occurred.

When to seek care

Make an appointment with your health care provider if you have signs or symptoms of kidney disease.

If you have a medical condition that increases your risk of kidney disease, your care provider is likely to monitor your kidney function with urine and blood tests and your blood pressure during regular office visits. Ask your provider whether these tests are necessary for you.

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Causes

Healthy kidney vs. diseased kidney

A typical kidney has about 1 million filtering units. Each unit, called a glomerulus, joins a tubule. The tubule collects urine. Conditions such as high blood pressure and diabetes harm kidney function by damaging these filtering units and tubules. The damage causes scarring.

Polycystic kidney

A healthy kidney (left) eliminates waste from the blood and maintains the body's chemical balance. With polycystic kidney disease (right), fluid-filled sacs called cysts develop in the kidneys. The kidneys grow larger and gradually lose the ability to function as they should.

Kidney disease occurs when a disease or condition impairs kidney function, causing kidney damage to worsen over several months or years. For some people, kidney damage can continue to progress even after the underlying condition is resolved.

Diseases and conditions that can lead to kidney disease include:

Type 1 or type 2 diabetes
High blood pressure
Glomerulonephritis (gloe-mer-u-low-nuh-FRY-tis) an inflammation of the kidney's filtering units (glomeruli)
Interstitial nephritis (in-tur-STISH-ul nuh-FRY-tis), an inflammation of the kidney's tubules and surrounding structures
Polycystic kidney disease or other inherited kidney diseases
Prolonged obstruction of the urinary tract, from conditions such as enlarged prostate, kidney stones and some cancers
Vesicoureteral (ves-ih-koe-yoo-REE-tur-ul) reflux, a condition that causes urine to back up into your kidneys
Recurrent kidney infection, also called pyelonephritis (pie-uh-low-nuh-FRY-tis)

Risk factors

Certain factors increase the risk that chronic kidney disease will progress more quickly to end-stage renal disease, including:

Diabetes with poor blood sugar control
Kidney disease that affects the glomeruli, the structures in the kidneys that filter wastes from the blood
Polycystic kidney disease
High blood pressure
Tobacco use
Black, Hispanic, Asian, Pacific Islander or American Indian heritage
Family history of kidney failure
Older age
Frequent use of medications that could be damaging to the kidney

Complications

Kidney damage, once it occurs, can't be reversed. Potential complications can affect almost any part of your body and can include:

Fluid retention, which could lead to swelling in your arms and legs, high blood pressure, or fluid in your lungs (pulmonary edema)
A sudden rise in potassium levels in your blood (hyperkalemia), which could impair your heart's ability to function and may be life-threatening
Heart disease
Weak bones and an increased risk of bone fractures
Anemia
Decreased sex drive, erectile dysfunction or reduced fertility
Damage to your central nervous system, which can cause difficulty concentrating, personality changes or seizures
Decreased immune response, which makes you more vulnerable to infection
Pericarditis, an inflammation of the saclike membrane that envelops your heart (pericardium)
Pregnancy complications that carry risks for the mother and the developing fetus
Malnutrition
Irreversible damage to your kidneys (end-stage kidney disease), eventually requiring either dialysis or a kidney transplant for survival