- Adams LG et al. (1994) Influence of dietary protein/calorie intake on renal morphology and function in cats with 5/6 nephrectomy. Lab Invest 70: 347-357.
- Barber PJ et al. (1999) Effect of dietary phosphate restriction on renal secondary hyperparathyroidism in the cat. J Small Anim Pract 40(2): 62-70.
- Dow SW et al. (1990) Effects of dietary acidification and potassium depletion on acid-base balance, mineral metabolism and renal function in adult cats. J Nutr 120: 569-578.
- Elliot J et al. (2000) Survival of cats with naturally occurring chronic renal failure: effect of dietary management. J Small Anim Pract 41: 235 – 242.
- Freeman LM et al. (2016) Evaluation of weight loss over time in cats with chronic kidney disease. J Vet Intern Med 30: 1661-1666.
- Harte JG et al. (1994) Dietary management of naturally occurring chronic renal failure in cats. J Nutr 124(12 Suppl): 2660S-2662S.
- IRIS, International Renal Interest Society (2023) Treatment Recommendations for CKD in Cats. http://www.iris-kidney.com/guidelines/recommendations.html
- Plantinga EA et al. (2005) Retrospective study of cats with acquired chronic renal failure offered different commercial diets. Vet Rec 157: 185-187.
- Ross LA et al. (1982) Effect of dietary phosphorus restriction on the kidneys of cats with reduced renal mass. Am J Vet Res 43: 1023-1026
- Ross SJ (2006) Clinical evaluation of dietary modification for treatment of spontaneous chronic kidney disease in cats. J Am Vet Med Assoc 229(6): 949-957.
Nutritional management of cats with chronic kidney disease
Diet plays a crucial role in managing CKD in cats. Dietary management can help slow the progression of the disease and extend survival time, alleviate clinical signs, and improve the quality of life. IRIS recommends to start feeding a clinical renal diet to cats with CKD in Stage 2. However, for cats with CKD Stage 1 with hypertension or proteinuria even earlier dietary adaptation to a sodium-restricted diet in case of hypertension or a renal diet in case of proteinuria is recommended (IRIS 2023).
Clinical trials with cats with naturally occurring CKD have shown that feeding renal diets with reduced phosphorus and protein levels reduced plasma levels of phosphorus, PTH, urea and creatine and was associated with reduced uremic episodes, less renal-related deaths, improved body condition and reduced clinical signs (Harte et al, 1994, Barber et al, 1999, Ross et al, 2006). Cats with CKD fed phosphorus- and protein-restricted renal diets also had a better quality of life and a longer median survival time (633 days in cats on a renal diet versus 264 days in cats on a control diet) (Elliot et al, 2000).
Omega-3 fatty acids can provide extra benefit to a kidney diet
Omega-3 fatty acids EPA and DHA, such as those found in fish oils, can be used as precursors for the body’s natural production of anti-inflammatory eicosanoids and mediators. These mediators can have beneficial effects on kidney function by reducing inflammation, blood pressure, platelet aggregation and hyperlipidaemia. In a retrospective study in cats with acquired CKD it was found that cats which were fed a kidney diet with a very high level of omega-3 fatty acid EPA from fish, survived considerably longer than cats fed a normal maintenance diet or a kidney diet without or with much lower levels of omega-3 fatty acids. For cats with CKD fed their regular maintenance diet the median survival time was 7 months, for all cats fed a renal diet 16 months, and for cats fed a renal diet with a very high level of EPA (0.47 g/MJ) the median survival time was 23 months (Plantinga et al, 2005).
Sodium reduction
CKD is often associated with hypertension. Pharmacological antihypertensive treatment can decrease proteinuria and a reduction in glomerular filtration rate, suggesting that prevention of hypertension may help to reduce progression of renal failure. As sodium-loading can induce hypertension, it is recommended to reduce sodium intake in kidney patients in combination with pharmacological therapy (IRIS 2023).
Maintenance of electrolyte and acid-base balance
Especially in later stages of CKD, the capacity to excrete acids or maintain electrolyte balance may be reduced, resulting in metabolic acidosis and hypokalaemia. Kidney diets can be specially formulated with alkalinizing agents to increase the dietary base excess to correct metabolic acidosis. Hypokalaemia is common in cats with CKD and can reduce renal function (Dow et al, 1990). An increase in the potassium level in kidney diets for cats can help to maintain a normal plasma potassium level.
Monitoring of renal patients
The dietary needs of cats with CKD may vary depending on the stage and severity of CKD, as well as any other medical condition they may have. Regular veterinary check-ups and assessment of the cat’s condition and nutritional needs are therefore important. Regular analysis of serum phosphorus concentrations indicate if the phosphorus level is within the IRIS target range or requires adaptation. When the plasma phosphorus is above the target range further restriction of dietary phosphorus is required or phosphorus binders can be used. If serum phosphorus is within the target range, measurement of FGF23 can indicate if the cat would benefit from further phosphorus restriction; the presence of hypercalcaemia indicates to switch to a diet with a less restricted phosphorus level or to reduce the dose of phosphorus binders (IRIS 2023). When blood levels of nitrogenous waste products are high, the dietary protein level may be further reduced (on the condition that the cat’s protein and amino acid needs are still covered) or special binders can be used, which bind protein by-products in the intestines so that these cannot be converted into uremic toxins. Regular monitoring is crucial to adjust the diet and further treatment as the disease progresses.
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