Chronic kidney disease (CKD) is a prevalent and increasingly common condition in the UK’s feline population, particularly affecting older cats. It is estimated that CKD impacts 30% of cats over 10 years of age and up to 80% of those over 15. The kidneys are vital organs responsible for filtering waste from the blood, regulating blood pressure, maintaining fluid balance, and controlling essential mineral and pH levels. The functional units of the kidney, known as nephrons, decline with age or disease, leading to reduced filtration and the buildup of waste products, a condition called azotaemia.
Differentiating Acute vs. Chronic Kidney Disease
Understanding whether kidney disease is acute or chronic is crucial for proper management.
| Acute Kidney Disease Symptoms | Chronic Kidney Disease Symptoms |
|---|---|
| Lethargy | Excessive thirst |
| Diarrhea | Excessive urination |
| Vomiting | Reduced appetite |
| Disorientation | Weight loss |
| Severe weakness | Urinary infections |
| Difficulty urinating | Vomiting and diarrhea |
Acute Kidney Disease (AKD) is a short-term condition characterized by a sudden onset of symptoms. Prompt medical and nutritional intervention can lead to a full recovery. AKD can be caused by decreased blood flow, ingestion of toxins (like antifreeze or rat poison), or harmful foods such as raisins or onions.
Chronic Kidney Disease (CKD), on the other hand, is a progressive illness where kidney function declines gradually. While it cannot typically be reversed, its progression can be managed and slowed with appropriate care.
CKD is classified into four progressive stages:
- Stage I: Kidney damage occurs, but elevated waste products are not yet detectable in the blood. There are usually no visible symptoms.
- Stage II: Waste filtration begins to decline further, with elevated waste products in both blood and urine. Physical symptoms are typically absent.
- Stage III: Kidney filtration continues to decrease, leading to significantly elevated waste products. Symptoms such as excessive thirst and urination may become apparent.
- Stage IV: Severe decline in kidney filtration causes toxins to build up in the blood, resulting in a wide range of physical symptoms including weight loss, vomiting, diarrhea, and lethargy.
Most cats do not exhibit physical symptoms until approximately 70–75% of their renal function is lost, typically by Stage III or IV.
Dietary Management for Cats with CKD
Dietary management is a cornerstone of caring for cats with kidney disease. Many veterinarians recommend a “prescription” kidney diet formulated with adjusted protein, phosphorus, and sodium levels. However, CKD can also be managed successfully with a raw diet, provided specific nutritional criteria are met. Key considerations include protein, phosphorus, moisture, and fat content.
Protein
Cats are obligate carnivores and naturally thrive on diets rich in protein and moderate in fat, with very few carbohydrates. Their natural prey consists of approximately 54% protein, 45% fat, and 1% carbohydrate. Protein quality, defined by its amino acid composition and digestibility, is higher in animal sources. Feeding highly digestible, quality animal protein is crucial for cats with CKD.
While protein restriction is sometimes debated, it’s important to note that in cats, unlike dogs with advanced CKD, high urine protein and creatine levels are uncommon. Protein restriction has not been definitively shown to slow disease progression in cats. Insufficient protein can lead to weight loss and negatively impact overall health. As obligate carnivores, cats require meat for energy, a need that doesn’t change with kidney disease. Restricting protein can cause muscle and organ wastage. Cats are unable to downregulate hepatic enzyme activity related to protein metabolism, making them particularly vulnerable to protein malnutrition.
Protein itself does not damage the kidneys; rather, the waste products from protein digestion can accumulate. In late-stage CKD, moderate protein restriction may help reduce nitrogenous waste and control proteinuria, but very low-protein diets are not advised. Research suggests that cats with CKD might even require more protein than typically found in prescription diets to prevent muscle loss.
The quality of protein impacts digestibility and the amount of waste produced. Higher quality proteins, such as those found in eggs and raw meat, yield less nitrogenous waste upon digestion. Therefore, a cat with kidney issues can consume a larger quantity of high-quality protein compared to low-quality protein without generating as much waste. Raw animal protein is ideal as it produces less nitrogenous waste than processed proteins that are more difficult to digest.
Phosphorus
Phosphorus is vital for DNA, RNA, cell membranes, and energy production. The body maintains phosphorus levels through intestinal absorption and kidney excretion. When kidney function is impaired, phosphorus can accumulate in the blood. Consequently, a lower phosphorus diet is recommended for cats with CKD to reduce the kidneys’ workload. Phosphate binders, such as calcium carbonate, can be used to further decrease phosphorus absorption by binding it in the food, offering more flexibility in feeding. Consulting your veterinarian is recommended to discuss these options.
It is important to distinguish between inorganic and organic phosphorus. Inorganic phosphorus poses a greater risk as it is more readily absorbed into the bloodstream, increasing the burden on the kidneys. Organic phosphorus is typically water-soluble and found naturally in raw animal and plant ingredients. Inorganic phosphorus is often added during food processing. In contrast, dietary phosphorus from natural food sources like meat and vegetables appears to have a less significant impact on post-meal plasma phosphorus levels.
Some low-phosphorus meats include chicken, rabbit, and duck. Medium-phosphorus meats include beef and turkey. The highest phosphorus foods are bones, dairy, and organ meats (especially liver). However, these can still be fed in moderation rather than being entirely avoided. Feeding fattier meats alongside moderate, high-quality protein is an effective strategy for managing phosphorus intake. For managing your cat’s diet, explore options like raw cat food.
Moisture
Adequate hydration is critical for all cats, especially those with kidney disease. Dry diets (less than 10% moisture) place a chronic strain on the kidneys, whereas raw or wet diets mimic the natural moisture content of prey (around 70%), supporting hydration and kidney health. Since cats have a low thirst drive, increasing dietary moisture is essential. Boosting dietary moisture from 10% to 75% can double urine volume, thereby reducing kidney strain and supporting urinary tract health.
Fats
Inflammation is a contributing factor to the progression of kidney disease. Diets high in carbohydrates and processed fats can elevate omega-6 levels, creating a pro-inflammatory state. Supplementation with omega-3 fatty acids, specifically DHA and EPA, has anti-inflammatory and renoprotective effects. Experimental studies indicate that DHA and EPA can reduce proteinuria in cats with late-stage CKD. Occasional salmon oil supplementation is a practical source of omega-3 for cats.
Criteria for a Raw Diet in Cats with CKD
In the early stages of CKD, a complete, fresh raw meat diet is optimal. As the disease progresses, you may need to adjust the diet by reducing its phosphorus content. In end-stage CKD, protein intake may also require moderation.
Palatability is a significant factor, especially in older cats. Circulating toxins and a reduced sense of smell can lead to decreased appetite, with inappetence affecting up to 92% of cats with CKD. Raw diets naturally enhance palatability due to their fresh fats and aromas, helping to maintain food intake. If you are considering a raw diet for your cat, investigate raw dog food options as well, as many principles apply to canine nutrition.
Fresh raw kidney is highly nutritious, particularly rich in water-soluble B vitamins, which are lost through increased urination in CKD. However, kidney should only constitute 3–5% of the diet to prevent excessive phosphorus intake.
For cats with advanced CKD, the diet should prioritize high-quality protein in moderate amounts and low phosphorus. Moderately restricted, high-quality protein helps reduce the kidneys’ workload and limits nitrogenous waste, which can exacerbate CKD symptoms. For owners seeking treats, consider raw meaty bones and dried treats as supplementary options.
Caring for a cat with CKD requires careful attention to diet and overall management. By understanding the disease and implementing appropriate dietary strategies, you can significantly improve your cat’s quality of life and slow the progression of the illness. Always consult with your veterinarian for personalized advice and treatment plans.
