Nutritional management of chronic renal failure (CRF) in cats

Chronic renal failure (CRF) is one of the most common and important diseases of older cats. The risk of CRF developing in cats over ten years of age increases approximately 4-5 fold, and the risk in cats over 15 years of age increases approximately 20 fold.

The International Renal Interest Society (IRIS)¹ has developed a four-stage classification of chronic renal disease:

• Stage 1 - Early renal disease: Renal disease/insults but no azotaemia (serum creatinine<140 µmol/l). May be reduced glomerular filtration and urine concentrating ability.
• Stage 2 - Early renal failure: Mild azotaemia (serum creatinine 140-249 µmol/l) with early/mild biochemical and clinical complications.
• Stage 3 - Uraemic renal failure: Moderate azotaemia (serum creatinine 250-439 µmol/l), and may be many signs of systemic complications present.
• Stage 4 - End stage renal failure: Severe azotaemia (serum creatinine>440 µmol/l) and increased risk of many signs associated with systemic complications, and uraemic crises.

Knowledge about the stages of renal disease may help both with prognosis, and prioritising further investigations and treatments. Although CRF is irreversible, appropriate intervention may help to:

• Limit additional damage to the kidneys (e.g., where an underlying cause can be treated).
• Slow the progression of disease and significantly enhance survival.
• Address complications that arise from the CRF (e.g., hypertension).
• Improve the quality of life for the patient.

Treatment and monitoring plans for cats with CRF always have to be adjusted according to the needs of the individual patient. However, appropriate dietary intervention is essential and because of its impact, there is no doubt that for most cats with CRF this represents the single most important therapeutic intervention^2,3.

As well as improving the quality of life for the cat, clinical studies have consistently shown that welldesigned dietary intervention for cats with CRF has the power to dramatically prolong survival and reduce adverse uraemic events.

Nutrition in cats with CRF can impact in numerous important ways.

• Dietary phosphate restriction (IRIS recommends restriction of dietary phosphate from IRIS renal disease stage 2 onwards):
  - reduces morphological damage to the kidneys,
  - helps prevent or minimise renal secondary hyperparathyroidism,
  - significantly contributes to improved longevity in CRF patients.
• Dietary protein restriction:
  - is not thought to have a major effect on longevity per se,
  - can dramatically reduce nitrogenous waste and uraemic toxins leading to significantly improved quality of life for CRF patients, if done appropriately.
• Dietary potassium:
  - CRF can lead to excessive loss of urinary potassium in cats.
  - Hypokalaemia can contribute to ongoing renal damage.
  - An appropriate diet will help maintain normokalaemia and address the cat's needs.
• Acid-base balance – CRF can lead to acidosis and an appropriate diet can help to minimise this risk.
• Other aspects – numerous other dietary components can help to manage the patient with CRF, including anti-oxidants (to reduce free radical associated renal damage); increased water-soluble vitamin concentrations to meet potential increased losses through diuresis; and increased concentrations of omega-3 fatty acids which appear to be renoprotective.

Feline NF is specifically designed to meet the precise needs of cats with renal failure:

• Low phosphorus levels to slow disease progression and renal damage.
• Low level, but highly digestible protein with high biological value to reduce signs of uraemia.
• Added potassium to address the increased needs.
• Non-acidifying to reduce the risk of acidosis.
• Added B-vitamins, omega-3 fatty acids and anti-oxidants.