Chronic kidney disease is seen in 28 to 31 percent of geriatric cats and 7 percent of dogs. While there’s no cure, many studies show dietary management with a therapeutic renal diet containing high-quality protein and reduced phosphorus can help to slow progression and give pets with CKD better quality of life by decreasing the body’s production of waste products and maintaining normal blood pressure.
“Data is available to show that nutritional intervention can improve both patient morbidity and mortality in dogs and cats with CKD,” said Martha Cline, DVM, DACVN, at Red Bank Veterinary Hospital in New Jersey.
But pets, cats in particular, don’t always buy into that, and managing them can be frustrating for veterinarians and owners alike. Here’s what to know about their nutritional needs and ways to meet the challenge of getting them to eat an appropriate diet.
Assessing a pet’s nutritional status
A nutritional assessment checklist for pets with CKD includes body weight, body condition score, muscle condition score, and any clinical signs associated with CKD that might affect diet choices.
Gary Marshall, DVM, of Island Cats Veterinary Hospital in Mercer Island, Wash., starts by looking at the cat. Is the weight ideal? Is weight increasing or decreasing? What is the cat’s body condition score, muscle condition score, hydration level, and coat quality? Does the cat appear to have pain in joints, the oral cavity or elsewhere in the body? What is the cat’s mental acuity?
Next, Dr. Marshall looks at blood parameters to see if chemistries and electrolytes are in balance and if anemia is present or the cat is dealing with concurrent hyperthyroidism. Urinalysis and blood pressure evaluation are other important factors in a complete renal workup. With this information in hand, he decides whether the cat is doing well on the current diet or if he should recommend a new diet.
|Staging CKD in cats and dogs|
|Guidelines for staging chronic kidney disease, including algorithms, are available from the International Renal Interest Society at iris-kidney.com. The international organization was created in 1998 to help veterinarians improve understanding, diagnosis, and treatment of renal disease in cats and dogs.
“The patient is staged according to fasted blood creatinine levels in a nondehydrated patient,” said Sarah Caney, BVSc, PhD, DSAM, of Vet Professionals Ltd. in the U.K. and author of Caring for a Cat with Chronic Kidney Disease. “Ideally, the test is repeated on at least two occasions so that an accurate assessment can be performed in the stable patient. Patients can then be sub-staged according to their blood pressure and proteinuria-UPC-measurements.”
IRIS staging can be a good starting point, but Gary Marshall, DVM, of Island Cats Veterinary Hospital in Mercer Island, Wash., finds it more useful to look at exam findings and patient symptoms in combination with trends in lab values.
“I have many patients who appear very sick with a creatinine of 2.8, and some who are quite stable and in good clinical shape with a creatinine of 4.8,” he said. “I think if the current popular staging protocol included muscle condition and trend in core lab data, it might be more helpful in assessing the patient in a holistic fashion. It is extremely difficult to accurately stage feline patients with only one set of data at one point in time.”
A complementary diagnostic in cats and dogs is SDMA concentrations in blood plasma or serum, which may be a more sensitive biomarker of renal function. The IDEXX SDMA assay, introduced in 2015, can help to identify CKD an average of 17 months sooner in cats, according to a study published in 2014 in the Journal of Veterinary Internal Medicine. Increased levels of SDMA in the blood are noticeable when only 40 percent of kidney function has been lost, as opposed to higher levels of BUN and creatinine, which may not become evident until 75 percent of kidney function is gone.
“SDMA levels are not influenced by muscle mass, and therefore levels can be more reliable in indicating the severity of renal disease in poorly muscled patients,” Dr. Caney said. “For example, if the patient has poor muscle mass and an SDMA of 25 or higher (SDMA ≥25 μg/dl), it is suggested they are treated as IRIS Stage 3, even if their creatinine levels are in the Stage 2 range.”
An SDMA test alone is not sufficient to diagnose or stage CKD. The test does not detect proteinuria, hypertension, and anemia, all factors affecting progression and survival. And dehydrated pets may have artificial elevations of SDMA.
“It is important for clinicians to remember the guidelines call for this test to be persistently elevated or in conjunction with additional clinical findings for the diagnosis of early CKD,” said Martha Cline, DVM, DACVN, at Red Bank Veterinary Hospital in New Jersey.
Therapeutic renal diets and home-prepared diets are options for feeding pets with CKD. Therapeutic diets can improve patient morbidity and mortality, but some animals may not find them palatable due to changes in appetite occuring with CKD, Dr. Cline said.
For pets who will eat it, a commercial TRD is preferable because it is nutritionally balanced, said Sarah Caney, BVSc, PhD, DSAM, of Vet Professionals Ltd. in the U.K. and author of Caring for a Cat with Chronic Kidney Disease. “The ideal diet is a wet formulation, if possible, to support maintenance of normal hydration,” she said.
While most papers indicate that azotemic patients in IRIS stages 2, 3, and 4 benefit most from a TRD, recent papers suggest that cats in IRIS stage 1 may also benefit from eating a phosphate-restricted food, Dr. Caney said.
In a 2002 randomized double-blinded clinical study of 38 dogs with stage 3 or stage 4 CKD, the group fed the TRD demonstrated improved quality and increased quantity of life. Dogs fed the renal diet survived at least 13 months longer than dogs in the control group.
When pets turn up their noses at TRDs, home-prepared diets formulated by a veterinary nutritionist or individual with similar training may be considered. They can be tailored to an individual patient’s needs and tend to be more palatable. A home-prepared diet can be helpful with patients in later stages of CKD who experience loss of appetite.
“In clinical practice, I have found appropriately formulated home-prepared diets for CKD useful in improving caloric intake,” Dr. Cline said.
When Marshall has clients who ask about giving their CKD cat a home-prepared diet, he refers them to the UC Davis Nutritional Support Service (nutrition.vetmed.ucdavis), but he prefers TRDs.
“Recently, we have been seeing more and more focus on palatability from the major brands, so there is a wider choice for our sick patients,” he said.
Animals who won’t eat TRDs or home-prepared diets or are losing weight can do well with feeding tubes, usually on a short-term basis. They not only deliver appropriate nutrition to achieve caloric goals, but also enable owners to administer medication without pilling a pet. Commercially available liquid TRDs pass easily down even narrow feeding tubes. Commercially available wraps make feeding tube maintenance easier, as well.
The main hurdle, Dr. Marshall said, may be persuading owners that the short anesthetic procedure to implant a feeding tube will have a net benefit for a sick companion. Potential complications, which should be discussed beforehand with clients, include managing infections or cellulitis.
Levels of phosphorus, protein, sodium, potassium, and fatty acids are all components to consider when selecting a renal diet for a pet. Based on current available evidence, some are more important than others, and they aren’t necessarily the ones thought to be of concern.
Phosphorus: When it comes to managing CKD, phosphorus is a key nutrient. Phosphorus retention, causing elevated serum phosphorus, is common in advanced CKD. Even within normal range, higher serum phosphorus increases risk of further renal damage, said Dottie Laflamme, DVM, PhD, DACVN, in her 2018 VMX lecture “Dietary Management in Feline CKD.”
Although evidence supports a benefit to controlling phosphorus levels in cats with CKD, no studies have been performed to identify an optimum concentration of dietary phosphorus for cats with CKD, she said. The current recommendation is to tailor phosphate restriction or phosphate binders to individual patients to achieve a serum phosphorus concentration in the low normal range.
Protein: Protein restriction in CKD patients is often thought to be important, but based on the available evidence, protein restriction is not warranted in cats or dogs with early CKD, Dr. Laflamme said. If a commercial renal diet is fed for its other benefits, the recommendation is to select a higher-protein option. In one study, cats fed a higher-protein diet had better inulin clearance and lower serum creatinine. They also maintained body weight better than cats fed a lower protein diet.
“Look for kidney diets that have more protein, while still restricting phosphorus,” Laflamme said. “I have been known to recommend feline renal diets for dogs with CKD due to the higher protein content.”
Sodium: Hypertension and proteinuria are common findings in pets with CKD, but severely restricting dietary sodium is not a necessary part of managing those conditions. Sodium restriction has been shown to activate the renin-angiotensin-aldosterone system (RAAS), which can contribute to muscle wasting. According to Dr. Laflamme’s proceedings, existing evidence does not support feeding sodium-restricted diets to cats with CKD.
Fatty acids: Currently, evidence supporting a benefit from fatty acids for cats with CKD is weak. One study of healthy cats fed a diet rich in n-3 PUFA found they had increased renal blood flow and GFR. There appear to be potential benefits from n-3 PUFA in dogs with CKD, including reduced proteinuria, decreased intraglomerular hypertension, maintenance of GFR, increased survival, and decreased renal lesions. Future research may show benefits for cats as well.
Potassium: Hypokalemia occurs in 20 percent to 30 percent of cats with CKD, as well as in dogs, but the condition may be masked until body stores are depleted. A nonacidifying diet with adequate potassium is important for renal function, but because hyperkalemia occasionally occurs in pets with CKD, it’s important to assess each patient individually and recommend potassium supplements as needed.
|How infected ticks affect canine CKD|
|Why annual screening for exposure is vital
By Melissa Beall, DVM, PhD
All dogs need to be screened annually for exposure to infected ticks
A new study reinforces the importance of detecting exposure
A blue dot on a comprehensive pet-side vector-borne disease screening test, which indicated exposure to infected ticks, can be quickly and easily followed up with routine blood work and urinalysis to determine if there is hidden (or underlying) tick-borne disease.
What are the next steps for a blue dot on an apparently healthy dog?
What else can veterinarians and pet owners do?
Melissa Beall, DVM, Ph.D. is medical affairs manager
Feeding finicky pets
Keeping CKD patients both happy and well fed is not always easy. It can be difficult to persuade cats and dogs to switch to a new food.
If possible, transition CKD patients to a TRD while the disease is in its early stages, when animals are more likely to have a better appetite and be more willing to switch foods. Send home samples of several recommended diets and let the pet choose the one it likes best. Reassess the pet’s condition, including how it likes the food, after it has eaten it for one to
For animals with a poor appetite, wait to reach for an appetite stimulant, Caney said. First, try to find and treat causes such as dehydration, electrolyte and acid-base imbalances, nausea or vomiting, and chronic pain from osteoarthritis or other conditions. Instruct owners to ensure the pet has a comfortable, safe place to eat, free of intrusion from other pets or children.
Other complications associated with CKD that can affect appetite are hyperphosphatemia and hypokalemia. Managing these conditions may help to improve appetite, Cline said.
Watch weight to know if a pet is benefiting from a TRD. If it is decreasing, something needs to change. It may be necessary to let the animal eat its preferred food and supplement with intestinal phosphate binders.
“We may need to forgo the diets we want for the cat for the one the cat prefers and then look to additional supplements or additives to accomplish the proper nutritional goals,” Marshall said.
As always, each pet has its own preferences.
“A therapeutic kidney diet may not always be a one-size-fits all for every patient with CKD,” Cline said. “When I am evaluating my patients, I look at IRIS staging, diet history, and physical exam parameters when making diet recommendations.”