Kidneys Part 3: Managing Chronic Kidney Disease
August 6, 2019
We know the basics of how kidneys are supposed to work and one way things can go wrong, so the last question is: Can we do anything about it?
We cannot fix kidneys affected by ckd. This is a progressive disease, and eventually the kidneys will fail. Our goal in the meantime is to manage any excesses and deficits that are secondary to ckd in order to slow progression and minimize clinical signs. Pets can maintain a good quality of life in what is called a compensated state of ckd (living with the disease but feeling well) for significant periods of time, often years.
Recall that the acronym NEPHRONS can help guide general principles of management. These guidelines represent the ideal world where your pet will eat a diet we recommend or tolerate receiving subcutaneous fluids (my cat won’t!), so we are always mindful of individualizing any plan to fit you and your pet.
The primary nutritional goal is for your pet to eat enough to maintain a healthy body weight. This can mean mixing up feeding strategies and/or foods as well as using anti-nausea, acid reducing, and/or appetite stimulant medications as needed. Specific diets may be recommended, more on that under “retention of wastes.”
The most commonly affected electrolyte level in ckd is potassium. It is most commonly too low (hypokalemia). Abnormal potassium can cause muscle weakness, poor appetite, or abnormal heart rhythms. We can supplement potassium orally.
Proteinuria (Protein in the urine)
In a subtype of kidney disease called protein-losing nephropathy or PLN, the kidneys lose or leak protein into the urine. This does not happen in all pets with ckd, but it is serious when it does because it may accelerate damage to kidneys and lead to dangerously low protein levels. Supplementing omega fatty acids may help, and medications called ACE inhibitors may be needed to manage proteinuria.
Because kidneys affected by ckd have lost the ability to conserve water, patients in all stages are prone to dehydration. It is extremely important to have access to plenty of fresh water available at all times. Feeding a canned diet and/or adding water or broth to food can help increase intake of fluids. We also frequently teach pet owners how to administer subcutaneous (under the skin) fluids or SQF at home to help pets maintain adequate hydration.
In addition, the effects of minor events like a hairball or getting into the garbage and having diarrhea can be much harder on these pets. Just a day of not feeling well and not eating/drinking normally can spiral into what we call an acute-on-chronic episode where rapid, severe dehydration makes pets feel very sick. So it is especially important to pay attention to your pets’ water intake during times of other illnesses or stresses.
Retention of Wastes
Increased levels of the wastes BUN, creatinine, and SDMA is called azotemia. Affected pets can live with some degree of azotemia without seeming to show any ill effects. At higher levels, however, azotemia can cause poor appetite, malaise, and vomiting.
Traditionally a low protein prescription diet is recommended because these wastes are by-products of protein metabolism; reducing protein can therefore reduce “garbage out” and minimize their levels. There is also evidence that a restricted protein diet can help slow progression, although studies are contradictory on this point. (Phosphorus may be the real culprit, but most foods that are low in phosphorus are also low in protein.)
However, it is much more important that your pet consistently eat and maintain a healthy body weight than to hyperfocus on the specific diet. Many pets happily eat the prescription diets (my dog Maisy loves them), but some won’t (my cat Gertie won’t touch them). It’s ok if your cat will only eat Fancy Feast. Being underweight and generally debilitated is much more problematic in the long run than the protein level of their diet.
Some people feel probiotics or prebiotics may help reduce azotemia, but there is little evidence to support this claim. However, they are not harmful. There are a wide variety of supplements and herbs on the market as well, and you can speak to one of the doctors if you have questions about a specific product.
Other Renal Insults – Avoid
We want to treat already compromised kidneys with care and not cause further damage. There are numerous drugs that we will not use or use at reduced doses in pets who are known to have ckd as they can further damage the kidneys. Dehydration can also further damage the kidneys, so it gets a mention here even though it had its own section.
Neuroendocrine (hormonal/neurotransmitter) Changes
Hypertension (high blood pressure) is commonly seen in cats with ckd, less commonly in dogs. We can usually manage hypertension with medication.
Anemia (too few red blood cells) may occur secondary to ckd due to either iron deficiency or too little of the hormone erythropoietin that the kidneys use to tell the bone marrow to make more red blood cells. Supplementing iron is relatively easy. There are synthetic versions of erythropoietin available, but treatment can be costly and labor intensive and details should be discussed with a doctor.
A rare complication is called renal secondary hyperparathyroidism. This happens when the system that regulates calcium and phosphorus (overseen by the parathryoid glands) becomes deranged in response to altered levels of calcium and phosphorus.
Even though pets with ckd go through long periods of stability, it is a progressive, dynamic disease and keeping an eye on both the primary kidney values (BUN, creatinine, SDMA) and potential complications (blood pressure, electrolytes, calcium/phosphorus, and red blood cells) helps us respond to changes in an individual’s needs. How frequently we recommend laboratory work depends on your pet’s stage of ckd, clinical signs, and current presence or absence of complications.
The take away messages for ckd are:
1. This is a chronic, progressive disease that is managed, not cured
2. There are several potential complications of ckd
3. Pets can maintain for months to years in a stable, compensated state with a good quality of life
4. There are a variety of interventions available to manage ckd and its complications which can be individualized for you and your pet
I have two pets living with ckd: My dog Maisy and my cat Gertie. Gertie was originally diagnosed 3-4 years ago and Maisy about a year and a half ago. Both are feeling well despite tolerating very different levels of intervention. So don’t panic if your pet receives this diagnosis, we will work with your to maintain the best quality of life for your pet.
Karen Christopherson, DVM CVA