Nutritional Management in a Senior Cat with Weight Loss

Figure The patient showing muscle and weight loss

THE CASE

A 14-year-old neutered male British Burmese cat (Figure) was presented for a routine geriatric examination. Although he had a good appetite, his weight had decreased from 10.1 lb (4.6 kg) to 9.1 lb (4.14 kg) over the past year.

History

The owner reported that the cat had become less active over the past year, had been sleeping on the floor instead of the couch as he had previously preferred, and may have been urinating increased volumes.

The patient’s diet comprised a combination of commercial adult maintenance dry cat food fed ad libitum and canned cat food fed at approximately 1.8 oz (≈50 g) per feeding twice a day. He had outdoor access only to a fenced garden; to the owner’s knowledge, the cat neither hunted nor scavenged. His appetite was good and unchanged over the past year.

The household included another cat, which was fed from a separate bowl; however, the cats often finished one another’s food, so the exact amount the presenting cat ate could not be determined.

Physical Examination 

The cat’s muscle condition score had not been evaluated or recorded the previous year, but mild-to-moderate muscle mass loss is currently evident. BCS, which was 7/9 the previous year, was 6/9 on examination. BCS is an estimate that was designed with healthy adult cats; elderly or ill cats may lose muscle mass (ie, sarcopenia) and retain fat (eg, inguinal fat pads) and therefore are more difficult to score accurately. 

The patient was bright and alert, with normal mucous membranes, thoracic auscultation, and abdominal palpation. Respiratory rate was 28 breaths per minute, and heart rate was 180 bpm with synchronous pulses. Blood pressure was 140 mm Hg. Rectal temperature was 100.6°F (38.1°C). He had decreased mobility because of previously diagnosed arthritis in both elbows; some joint thickening was noted, but no crepitus was observed.

Diagnostic Results

Hematology results were within reference ranges. 

Urine specific gravity was 1.029; dipstick results were negative for all parameters. Urine culture results were negative. Urine protein:creatinine ratio was 0.18 (reference range, <0.2). Abnormalities in the serum chemistry profile included elevated blood urea nitrogen and elevated glucose without glucosuria (Table). Fructosamine levels were within reference range.

Serum Chemistry Results

Elevated serum glucose without glucosuria and fructosamine within the reference range is likely a transient rise from stress. Because British Burmese are at risk for diabetes mellitus, fructosamine evaluation was possibly justified, although the glucose value is not consistent with polyuria and/or polydipsia resulting from diabetes mellitus.

The patient’s mild azotemia was likely due to prerenal causes (eg, subclinical dehydration), early kidney disease, or both.

DIAGNOSIS:

CHRONIC KIDNEY DISEASE & PRESUMPTIVE OSTEOARTHRITIS

In addition to osteoarthritis, the patient was diagnosed with International Renal Interest Society (IRIS) Stage 1, nonproteinuric, normotensive chronic kidney disease (CKD).¹ 

Cats with early-stage CKD may be able to concentrate urine more than a dog at the same stage; therefore, the cat’s urine specific gravity did not rule out CKD.

Nutritional Management

Nutritional management can be more challenging in senior pets (ie, those >7 years of age) because they often have several concurrent disorders; however, nutritional management should be considered for senior patients with CKD and weight loss and may be helpful in arthritis cases. Nutritional management for feline IRIS Stage 1 CKD is less clear-cut than for later stages, but there are some key guidelines (see Feline IRIS Stage 1 CKD Guidelines).¹

Recommendations vary regarding dietary phosphorus restriction in patients with early CKD; however, the diet should not be high in phosphorus. A nonacidifying, low-sodium diet with increased water-soluble vitamins is appropriate. Although low-sodium diets are not associated with hypertension in cats, high salt is associated with hypokalemia and possibly an increase in serum creatinine, blood urea nitrogen, and phosphorus. The amount of protein to provide at IRIS Stage 1 is controversial. This patient—like many older cats—has muscle loss, so restriction should initially not be excessive, and a high-quality protein (ie, with a high percentage of essential amino acids) should be fed.² Omega-3 fatty acids may help improve survival time in patients with CKD,³ improve arthritis signs,⁴ and improve cognition in older cats.⁵

Transitioning to a new diet should be done slowly, with both the old and new diets offered initially. For this patient, the diets were mixed; however, some clinicians may recommend offering each diet separately based on the proportions an individual cat will accept. In some cases, it may take weeks to transition a cat to a new diet. Warming a canned diet to just below body temperature may be helpful. Maropitant can help with nausea and vomiting, and mirtazapine can help stimulate appetite.

For this patient, a commercial diet formulated for older cats is appropriate. A senior diet can be a good transition diet for cats with early stages of CKD. Many senior diets are lower in phosphorus and sodium and are less acidic than maintenance diets. Potassium content should be high, as there will be increased renal loss. Antioxidants are often added to help enhance immune and cognitive function and increase longevity. Oxidative damage may be present in renal disease, and antioxidants may have a beneficial effect on this stress.⁶

A diet with functional lipids (fish oil), antioxidants (vitamins C and E), l-carnitine, botanicals (vegetables), highly bioavailable protein, and amino acid supplements was shown to improve symmetrical dimethylarginine (SDMA) in older cats.⁷ A dose of EPA and DHA of 50-100 mg/kg has been suggested, as long as it does not affect diet palatability.⁷ Older cats should have an energy-dense diet (4-4.5 kcal/g dry matter). Caloric intake should only be restricted in obese cats.

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Diet in Disease is a series developed by the WSAVA, the Academy of Veterinary Nutrition Technicians, and Clinician’s Brief.