Introduction

Chronic kidney disease (CKD) is the most common renal disease in the cat. The prevalence of CKD seems to be increasing over time; estimates are that it affects about one-third of all cats over 15 years of age. It is an important cause of mortality, especially in older cats. CKD is typically a progressive disease and can be accompanied by a wide range of clinical and pathological changes. However, the clinical presentation is variable from patient to patient.

The International Renal Interest Society (IRIS) has published guidelines for clinical staging and treatment targets for both canine and feline kidney disease (www.iris-kidney.com). As well, the International Society of Feline Medicine published ISFM Consensus Guidelines on the Diagnosis and Management of Feline Chronic Kidney Disease in 2016 (https://journals.sagepub.com/doi/pdf/10.1177/1098612X16631234). The reader is referred to these documents for a complete discussion of CKD diagnosis and management.

The goals of CKD therapy are to:

• Minimize clinical signs of uremia
• Minimize disturbances of electrolytes, vitamins, and minerals
• Provide adequate nutrition and hydration
• Improve quality of life (QOL), especially in International Renal Interest Society (IRIS) stages 3 and 4
• Modify disease progression

Wherever possible, potential therapies should be evaluated considering a specific treatment goal and based on available evidence. In some patients, multiple treatments may be indicated, but administration of multiple therapies must be balanced with QOL—prioritizing therapies most likely to benefit each patient is important.

This session will focus on keeping CKD cats well hydrated and nourished as it is critical for their survival and well-being.

Importance of Dietary Management

The use of diets specifically formulated for CKD results in improved survival and quality of life.¹

The key nutritional factors in CKD diets for cats are as follows²: phosphorus restriction, high quality protein moderation, sodium control, B vitamin fortification and alkalization (the only feline diets to promote so). The potassium content is usually higher than typical maintenance diets, although it varies from brand to brand. Some of them also include long chain omega 3 fatty acids EPA and DHA.

Energy

Cats with CKD have typically waxing and waning appetite, which is why CKD diets are energy dense (high fat, low fiber). These diets are high in energy density (thus, low in fiber and high in fat) to promote adequate energy intake even in the face of occasional inappetence. Both dry and canned use this strategy, but canned foods, by virtue of their high moisture content, are less energy dense than dry foods.

Phosphorus

The most important modification in CKD diets is phosphorus restriction (below 1 g/1000 kcal, in general), which is indicated to address renal secondary hyperparathyroidism, and this strategy is believed to slow down progression of CKD. The IRIS society (www.iris-kidney.com) recommends the use of low phosphorus diets initially (stage II onwards), but recommends the addition of phosphate binders at later stages, where dietary restriction is not enough.

Sodium

These diets have moderate sodium concentrations as a precaution due to the likelihood of hypertension in these patients, although the effect of dietary sodium on blood pressure is unclear. Sodium is never truly restricted, because a very low sodium diet can stimulate the renin angiotensin aldosterone axis and result in hypertension.³ Most maintenance diets provide 1 g/1000 kcal, and renal diets range from 0.5 to 1 g/1000 kcal.

Potassium

Potassium content varies amongst feline CKD diets (from 1.5 to 3.5 g/1000 kcal, approximately). In hyperkalemic patients (e.g., some patients treated with ACE inhibitors), choosing the lowest K diet available is indicated. For hypokalemia, high K diets can be chosen (or, alternatively, potassium can be supplemented orally).

Protein

Protein should never be restricted. Providing all nitrogen and essential amino acids is essential and protein deficiency will result in lean mass loss and worse prognostic. Diets for CKD are always above the requirement, but they tend to be lower than typical maintenance diet to minimize nitrogen waste product formation and accumulation, which contribute to uremia. Dietary protein should be of a high biological value. Protein moderation then helps reduce clinical signs but it is not believed to affect progression (except potentially in proteinuric patients).

The NRC⁴ minimum protein requirement is around 16% protein calories, while AAFCO recommends maintenance feline diets provide at least 22%. Thus, protein intake will be adequate provided that the patient meets its energy needs. If the cat does not eat enough calories, muscle mobilization will happen and both body and dietary protein will be used to obtain energy, resulting in protein:calorie malnutrition.

Feline CKD diets range from 22–34%, and all of them provide all amino acid requirements, thus there is a wide range to choose from for each specific case and adjusted to the stage of disease.

B Vitamins & Acid Base Balance

B vitamin losses can be increased due to polyuria, and inappetence can result in a decreased daily intake.

Kidneys are very important for acid base balance, and cats with CKD are prone to metabolic acidosis, which is why feline CKD diet are alkalinizing.

Omega-3 Fatty Acids

EPA and DHA have shown positive effects on experimental canine CKD, and one retrospective study in cats suggested that diets rich in these fatty acids could result in longer survival.⁵

Managing Hydration

Cats with CKD are predisposed to dehydration, especially in IRIS stages 3 and 4. Studies confirming the clinical impact of maintaining hydration are lacking, but it is considered a critical part of management. Maintaining hydration may help maintain QOL, address electrolyte and acid-base disturbances, and preserve renal blood flow by preventing dehydration (and potentially affecting disease progression). Unstable or decompensated cats with CKD may require hospitalization and intravenous (IV) fluid therapy, along with management of electrolyte and acid-base disturbances. Owners should also be educated about long-term management of hydration, including increasing voluntary water intake and home subcutaneous (SC) fluid therapy (75–150 ml every 1–3 days).⁶ Fluid choices include balanced electrolyte solutions or 0.45% saline. Potassium chloride can be added if needed to treat hypokalemia.

Managing Nausea and Inappetence

Cats with CKD may have nausea, vomiting, and inappetence because of uremic toxins affecting the central chemoreceptor trigger zone. Owners identify poor appetite as an important QOL concern; it could also result in protein and calorie malnutrition. A reduction in appetite should be actively investigated and treated—nausea should always be considered as a possible cause even if the cat is not vomiting. Maropitant (1 mg/kg PO every 24 hours) has been shown to reduce vomiting⁷ and mirtazapine (1.88 mg/cat PO every 48 hours) has been shown to reduce vomiting, increase appetite and promote weight gain.⁸ Other effective antiemetic drugs include ondansetron (0.5–1 mg/kg, IV, SC or PO every 8 hours)⁹ and dolasetron (0.6–1 mg/kg, IV, SC or PO every 24 hours). While hyperacidity may occur in some cats with CKD, gastric ulceration is typically not found. Instead, gastric mineralization and fibrosis are the most significant lesions.¹⁰ If therapy for hyperacidity is considered, omeprazole (1 mg/kg PO every 12 hours) is superior to famotidine.^11,12 Cats that are not achieving adequate food intake with drug therapy may benefit from placement of an esophagostomy feeding tube to maintain hydration, administer drugs and provide nutrition.

Nutritional Plan

A complete nutritional evaluation (https://www.wsava.org/guidelines/global-nutrition-guidelines) should be carried out before making recommendations. These recommendations should include:

1.  When to start dietary management:

a.  The recommendation is to change to a CKD diet in stages II to IV. Patients with stage I only require diet change if they present proteinuria, where they will benefit from a moderate protein diet. Earlier change will result in better acceptance.

2.  What to feed:

a.  There are several commercial feline CKD diets, choice will depend on stage of disease, price, availability, palatability, and nutrient characteristics.

3.  How much to feed:

a.  The amount of food should be enough to maintain a stable body weight and ideal body condition score (BCS). Label instructions are a good start but they will need twice a month adjustments. Patients with low BCS should be fed 20% more than label instructions/formulas.

4.  How to feed:

a.  Multiple small feedings or ad libitum feeding is indicated in thin patients. Overweight cats should be fed portion-controlled amounts to at least prevent further weight gain. Feeding tubes can be used in patients that are not eating enough to provide an adequate diet (plus medications and water).

Summary

For each CKD patient, the IRIS stage should be established and an individual treatment plan should be developed, considering what is most appropriate for each patient and owner. The options should be prioritized based on the cat’s medical needs and the owner’s preferences and abilities. The plan should be reviewed with the owners and their commitment confirmed. A reassessment and monitoring schedule should be established to assess the patient’s response, make any necessary changes to the treatment plan, ensure the owner understands the treatments and uncover compliance issues.

References

1.  Ross SJ, Osborne CA, Kirk CA, Lowry SR, Koehler LA, Polzin DJ. Clinical evaluation of dietary modification for treatment of spontaneous chronic kidney disease in cats. J Am Vet Med Assoc. 2006;229(6):949–957.

2.  Elliott DA. Nutritional management of chronic renal disease in dogs and cats. Vet Clin North Am Small Anim Pract. 2006;36:1377–1384.

3.  Buranakarl C, Mathur S, Brown SA. Effects of dietary sodium chloride intake on renal function and blood pressure in cats with normal and reduced renal function. Am J Vet Res. 2004;65(5):620–627.

4.  National Research Council. Nutrient Requirements of Dogs and Cats. Washington DC: National Academies Press; 2006.

5.  Plantinga EA, Everts H, Kastelein AM, Beynen AC. Retrospective study of the survival of cats with acquired chronic renal insufficiency offered different commercial diets. Vet Rec. 2005;157(7):185–187.

6.  Sparkes AH, Caney SMA, Chalhoub S, et al. ISFM Consensus guidelines on the diagnosis and management of feline chronic kidney disease. J Feline Med Surg. 2016;18(3):219–239.

7.  Quimby JM, Brock WT, Moses K, et al. Chronic use of maropitant for the management of vomiting and inappetence in cats with chronic kidney disease: a blinded placebo-controlled clinical trial. J Feline Med Surg. 2015;17(8):692–697.

8.  Quimby JM, Lunn KF. Mirtazapine as an appetite stimulant and anti-emetic in cats with chronic kidney disease: a masked placebo-controlled crossover clinical trial. Vet J. 2013;197(3):651–655.

9.  Quimby JM, Lake RC, Hansen RJ, et al. Oral, subcutaneous, and intravenous pharmacokinetics of ondansetron in healthy cats. J Vet Pharmacol Ther. 2014;37(4):348–353.

10.  McLeland SM, Lunn KF, Duncan CG, et al. Relationship among serum creatinine, serum gastrin, calcium-phosphorus product, and uremic gastropathy in cats with chronic kidney disease. J Vet Intern Med. 2014;28(3):827–837.

11.  Parkinson S, Tolbert K, Messenger K, et al. Evaluation of the effect of orally administered acid suppressants on intragastric pH in cats. J Vet Intern Med. 2015;29(1):104–112.

12.  Šutalo S, Ruetten M, Hartnack S, et al. The effect of orally administered ranitidine and once-daily or twice-daily orally administered omeprazole on intragastric pH in cats. J Vet Intern Med. 2015;29(3):840–846.