Renal dysplasia (RD), also known as renal malformation, refers to a type of congenital chronic kidney disease. It’s present at birth but usually takes weeks or months for an owner to suspect a problem. The affected kidney or kidneys are usually abnormally small, with a diminished renal cortex and immature glomeruli (the structures that remove waste from the blood.) The nephrons, which are the urine-producing structures, are also malformed. Unfortunately, the condition’s effects are progressive and can be fatal.
Once known as juvenile renal dysplasia, that name is a misnomer because the condition kills more dogs over the age of 5 years than puppies. The age at which signs appear is variable depending on the severity of the problem, and whether one or both kidneys are affected. Adults up to 10 years old can be initially diagnosed with the condition even though they had a mild malformation since birth.
What Are the Signs of Renal Dysplasia in Dogs?
The initial signs of renal dysplasia are the typical signs of kidney failure: increased thirst and increased urination.
As kidney failure progresses, additional signs may appear, including:
- Decreased appetite
- Weight loss
- Lethargy
- Bad breath
- Vomiting
- Oral ulcers
- Poor coat
- Jaw pain and disfigurement
How Is Renal Dysplasia in Dogs Diagnosed?
While owners rarely suspect renal failure, they may take their puppy to the veterinarian complaining of housebreaking problems. The veterinarian will perform a full physical examination, blood work, and urinalysis. The results will often indicate that the kidneys aren’t functioning properly, and can discriminate between some causes of kidney failure.
Blood chemistry profiles routinely test for two waste products that correlate with kidney function: blood urea nitrogen (BUN) and creatinine. Unfortunately, by the time these levels rise above the normal range, the kidneys have already lost about 75% of their function. A newer test called the symmetric dimethylarginine (SDMA), can detect kidney disease much earlier, when the kidneys have lost about 40% of their function.
Your veterinarian can then use ultrasound and radiographs to visualize the size and shape of the kidneys, indicating if one or both are involved and to what extent. In some cases, they may also perform a surgical biopsy. This will typically show underdeveloped glomeruli. The percentage of immature glomeruli in the biopsy sample is used to predict the severity of the disease. However, a biopsy may not be accurate in a young puppy because the kidney may not be fully mature up to 3 months of age, even in normal puppies.
In severe forms of RD, over 25% of the glomeruli are affected. These puppies will fail to thrive, may have stunted growth, and usually die of kidney failure between 3 and 6 months of age.
In moderate forms, in which 10% to 25% of the glomeruli are affected, the puppy will take longer to show signs of kidney failure. These puppies may also have stunted growth, but not as noticeably. Initial signs of kidney failure, such as increased thirst and urination, may go unnoticed or be attributed to housetraining failures. These puppies typically live for one to three years but usually need supportive care to do so.
Some cases are mild, with less than 10% of the glomeruli affected. These may not produce signs of kidney failure for years, if at all.
The International Renal Interest Society (IRIS) guidelines use the results of blood work to determine what stage of kidney failure a dog is in, from Stage 1 (mild) through 4 (advanced). Ultrasound of the kidneys can also be useful for staging disease. These stages can determine which treatment is most appropriate.
Is Renal Dysplasia Hereditary?
Renal dysplasia occurs more often in certain breeds, especially Shih Tzu and Lhasa Apsos but also Alaskan Malamutes, Bedlington Terriers, Chow Chows, Cocker Spaniels, Doberman Pinschers, Keeshonden, Nederlandse Kooikerhondje, Miniature Schnauzers, Norwegian Elkhounds, Samoyeds, Shetland Sheepdogs, Soft Coated Wheaten Terriers, and Standard Poodles. However, the condition can occur sporadically in any breed.
Because it occurs more often in some breeds, it’s assumed to have a hereditary component. However, when kidney failure occurs in a young dog of a breed not known for renal dysplasia, it leaves the breeder questioning whether renal dysplasia could be responsible. This is where a kidney biopsy could be important.
“A biopsy probably won’t make much difference to the affected individual,” explains Wendy Brooks, DVM, DABVP, Medical Director of Mar Vista Animal Medical Center in Los Angeles, California. “But it would make a difference with regard to the breeding of the parents. There are a lot of reasons to have kidney failure, but having a hereditary/genetic reason would likely end the breeding career of a potentially valuable animal, so you would want to be sure.”
In some breeds, a diagnosis of renal dysplasia, especially in more than one related puppy, could be a reason for not breeding parents or littermates. In other breeds, the condition may be so common there’s no choice. Shih Tzu have an especially high incidence of renal dysplasia. In a study examining biopsy results of 74 random Shih Tzu in North America, 84% had some evidence of renal dysplasia. The high percentage suggests it has a genetic component with variable penetrance. A 1990 breeding study found a recessive pattern of inheritance. However, a 10-year breeding study of Shih Tzu reported in 2003, found no obvious pattern of inheritance. The pattern was most consistent with autosomal dominance with incomplete penetrance.
It’s unknown if the same processes are responsible for renal malformation in different breeds, or if different processes may be responsible for similar outcomes. It’s also not known if the same genes might be responsible in different breeds. In one study of a family of Boxers, the condition was consistent with having a recessive mode of inheritance.
How Is Renal Dysplasia in Dogs Treated?
A diagnosis of renal dysplasia isn’t necessarily a death sentence. “Some individuals are affected more mildly,” says Brooks. She points to the study showing a large percentage of Shih Tzu that are diagnosed by biopsy. “A number of them were expected to remain asymptomatic because they were only mildly affected. Others could be expected to live for years. Another study showed a range of life spans with renal dysplasia from 7 weeks to 9 years. For most dogs, renal failure/kidney insufficiency will be evident in the first year of life, however,” she explains.
While RD is incurable, you can manage the condition in ways to reduce the workload on the kidneys, and thus increase your dog’s quality of life and lifespan.
Increase Hydration
The first rule is that you must keep your dog hydrated. Don’t withhold water, even if it means your dog is having accidents in your house. You want to do everything you can to encourage your dog to drink more. Extra fluid helps the kidneys flush out wastes, which is why one symptom of kidney failure is increased drinking and urination. Adding ice or chicken broth to the water may encourage your dog to drink more. But at some point, your dog simply can’t drink enough to adequately flush their kidneys. This is where intravenous (IV) or subcutaneous (SQ) fluids can help. Your veterinarian can administer IV fluids if your dog has an acute episode, but they’re not a long-term solution. You can, however, learn to administer SQ fluids at home. It’s simple once you get the hang of it, takes about 20 minutes a day, and can go on for years, as long as your dog is still responding.
Look at Their Diet
The second rule is that you have to modify your dog’s diet to compensate for the failing kidney function. A kidney-friendly diet controls phosphorus, sodium, and protein.
Phosphorus in Your Dog’s Diet
Phosphorus levels are very important. Phosphorus in food combines with other substances in the body to form phosphate compounds that circulate in the blood. Failing kidneys can’t eliminate enough phosphate from the body. They also can’t produce sufficient calcitriol, which regulates calcium and phosphate absorption to create the proper balance of them. When too much phosphate compared to calcium is in the bloodstream, the body pulls calcium from the bones to achieve the necessary balance, then mineralizes soft tissue to make up for the bone loss. This occurs most noticeably on the jaw, which becomes enlarged, weakened, and painful. The technical term for the condition is renal secondary hyperparathyroidism, but it’s sometimes referred to as “rubber jaw.”
Excess phosphate also affects the kidneys themselves. In one study comparing the effects of dietary phosphorus levels in dogs with kidney disease, only 33% of the group fed a high phosphorus diet survived after two years, compared to 75% of the group fed a low phosphorus diet.
Phosphorus is high in dairy products, bones, beans, peas, and nuts, so avoid these foods if possible. Phosphorus (or phosphate) binders given at mealtimes can prevent some ingested phosphorus from being absorbed in the intestines, but binders alone cannot counter the effects of a high-phosphate food.
Sodium in Your Dog’s Diet
Sodium levels should be moderately low. Many dogs with kidney failure develop high blood pressure, which can further damage the kidneys. A diet with moderately low sodium is optimal. Avoid high-sodium foods, such as cheese, fast foods, and cured meats, such as bacon, ham, and other lunch meats.
Protein in Your Dog’s Diet
Protein level and quality are very important. </strong>Kidney diets have traditionally been as low in protein as possible, but that has been called into question recently. The reason to keep protein low is that failing kidneys allow urea, which is a byproduct of protein metabolism, to build up in the blood. This makes dogs feel sick. That’s why the blood urea nitrogen (BUN) is used as one index of kidney function. Decreasing dietary protein can decrease the BUN, but has limits. If the protein level is too low, the body simply draws on its own protein source, its own muscles. Rather than abruptly switching to a low-protein diet, it’s preferable to match the protein level to the stage of kidney disease, reducing the protein as the disease progresses.
Protein sources with high biological value are better choices, as they produce fewer waste products. Egg protein has the highest biological value, followed by milk, meats, soybeans, and grains. Tofu (from soybeans) has a lower biological value but has the advantage of lower sulfur, which is also desirable.
Dietary Fatty Acids
Dietary fatty acids appear to affect kidney function and survival rate, but the fat source is important. Dogs with kidney failure that were supplemented with fish oil, and to a slightly lesser degree, beef tallow, had a much longer survival time than those supplemented with safflower oil. Salmon oil (fish body, not liver) is generally suggested because of the ratio of omega-6 to omega-3 fatty acid, which should be less than 2.5:1. A maximum of 1000 mg per 10 pounds of body weight is suggested.
As the BUN rises (which it will as the disease progresses), appetite decreases, so it’s important to make foods tasty.
Puppy-Specific Diets
Puppy diets may need to be modified to accommodate the special nutritional needs of a growing dog, especially if the puppy is a large breed. Each diet must be individualized depending on the puppy’s kidney staging, age, and potential growth. Compromises will likely need to be made; for example, more protein, phosphorus, and calcium may be necessary for growth than is optimal for renal disease.
If this all sounds daunting, don’t worry. That’s why veterinary prescription diets formulated for kidney disease exist. You can also find various recipes for home-prepared diets online.
Consider Drug Therapy
Medications include phosphorus binders, ACE inhibitors, erythropoietin, and appetite stimulants:
- Phosphorus binders are given with meals to decrease the amount of phosphorus available in the food.
- Angiotensin-converting enzyme (ACE) inhibitors may be prescribed to reduce blood pressure if needed.
- Erythropoietin may be given occasionally to promote red blood cell production, which may be deficient as kidney function decreases.
- Calcitriol supplementation may help protect the kidneys in dogs with stage 2 kidney failure.
- Appetite stimulants, anti-nausea drugs, and gastric acid-blocking drugs may be necessary as the disease progresses to encourage the dog to eat.
What About a Kidney Transplant or Dialysis?
Kidney transplants are possible, but they aren’t always successful. In fact, more are unsuccessful than successful. They also require a highly trained specialist, are very expensive, require a lot of medications and home care afterward, and entail some ethical concerns about taking a kidney from another dog.
Dialysis or continuous renal replacement therapy (CRRT), which is similar to dialysis but performed over 24 to 48 hours, may be options but are generally used for dogs in acute kidney failure rather than chronic.
“Transplants are just not working out well for dogs, and you need a littermate to get a decent tissue match (and good luck getting an unaffected littermate),” says Brooks. “Dialysis might work, but it is very expensive, and the dog has to be of a certain size. There is also CRRT, which might also work, but these treatments are very expensive.”
Managing a dog with kidney dysplasia and resultant kidney failure is complicated but doable. However, there are limits to the treatment options, depending on the severity of dysplasia. You’ll need ongoing advice from your veterinarian, as the steps you take will change as the disease progresses. Consider consulting with an internal medicine specialist. In addition, the Canine Kidneys group on Facebook has an abundance of information available in their files and from experienced members who’ve been in your situation.
This article is intended solely as general guidance, and does not constitute health or other professional advice. Individual situations and applicable laws vary by jurisdiction, and you are encouraged to obtain appropriate advice from qualified professionals in the applicable jurisdictions. We make no representations or warranties concerning any course of action taken by any person following or otherwise using the information offered or provided in this article, including any such information associated with and provided in connection with third-party products, and we will not be liable for any direct, indirect, consequential, special, exemplary or other damages that may result, including but not limited to economic loss, injury, illness or death.