Chronic kidney disease (CKD) in cats involves a progressive and irreversible decline in kidney function. The kidneys are organs responsible for filtering waste products from the blood, regulating mineral levels, maintaining hydration, and producing urine. CKD is common in older cats, affecting an estimated 30-40% over 10 years and up to 80% over 15. The disease often develops gradually, with noticeable signs appearing only after a significant portion of kidney function has been lost.
Signs and Symptoms of Kidney Disease
Observing changes in a cat’s behavior or physical condition can indicate kidney issues. Early indications often include increased thirst and urination. This happens because impaired kidneys struggle to concentrate urine, causing the cat to drink more to compensate for diluted urine. Subtle changes like a decline in coat quality or gradual weight loss may also be early signs.
As the disease progresses, more pronounced symptoms emerge due to waste product accumulation that kidneys can no longer filter. Cats might develop a reduced appetite, lethargy or decreased activity. Vomiting can become a regular occurrence, and a distinctive unpleasant odor may be noticed. Other later signs can include muscle weakness and pale gums, which may signal anemia due to the kidneys’ diminished ability to produce a red blood cell hormone.
Diagnosis and Staging
When kidney disease is suspected, a diagnostic process begins. Blood tests are a standard approach, with specific markers showing kidney function. Creatinine, a waste product, and Blood Urea Nitrogen (BUN), a byproduct of protein breakdown, are commonly measured. Elevated levels indicate that the kidneys are not effectively filtering waste, though significant increases often occur only after about 70-75% of kidney function has been lost.
A more sensitive indicator, Symmetric Dimethylarginine (SDMA), is important for earlier detection. SDMA levels can rise when about 40% of kidney function is impaired, before creatinine or BUN show abnormalities. This early elevation allows for prompt intervention to slow disease progression. SDMA levels above 14 µg/dl suggest kidney compromise, and unlike creatinine, it is less affected by a cat’s muscle mass or diet, providing a more reliable measure.
Alongside blood work, a urinalysis provides information about kidney concentrating ability and protein loss. Urine specific gravity (USG) measures urine concentration; in cats with CKD, kidneys lose their ability to concentrate urine, resulting in a low USG, often below 1.035. The urine protein:creatinine ratio (UPC) assesses proteinuria, leakage of protein into the urine, indicating damage to the kidney’s filtering units. A UPC ratio greater than 0.4 suggests significant protein loss and a less favorable long-term outlook.
Veterinarians use the International Renal Interest Society (IRIS) staging system to classify the severity of CKD and to guide treatment. This system categorizes the disease into four stages based on creatinine and SDMA concentrations, with substaging for proteinuria and blood pressure. Stage 1 involves subtle kidney abnormalities, potentially with elevated SDMA but normal creatinine, and no clinical signs. Stage 2 shows mild increases in creatinine (1.6-2.8 µg/dl) and/or SDMA (18-25 µg/dl), with signs often absent or mild.
As the disease progresses to Stage 3, creatinine levels range from 2.9-5.0 µg/dl and SDMA from 26-38 µg/dl, and cats may exhibit signs like lethargy or poor appetite. Stage 4 represents advanced disease, with creatinine exceeding 5.0 µg/dl and SDMA over 38 µg/dl, accompanied by more severe clinical signs. This structured approach helps veterinarians tailor management plans to each cat’s condition, aiming to slow progression and improve well-being.
Treatment and Management Strategies
Managing chronic kidney disease in cats focuses on slowing its progression and maximizing their comfort. Dietary modifications are a primary component of this management. Therapeutic kidney diets are formulated for cats with this condition. These diets are restricted in phosphorus, which helps slow disease advancement and improve well-being.
The protein content in these diets is also managed, being reduced but high quality to minimize the buildup of nitrogenous waste products that contribute to signs like vomiting and lethargy, while still preventing muscle loss. Some formulations include omega-3 fatty acids for kidney protection and increased potassium to counteract urinary losses. These specialized diets often lead to longer survival times.
Maintaining adequate hydration is important for CKD management, as affected kidneys cause increased water loss through dilute urine. Encouraging water intake through multiple fresh water sources, like fountains or adding water to wet food, can help. When oral hydration is insufficient, veterinarians may instruct owners on administering subcutaneous (SQ) fluids at home. These fluids are given under the skin and slowly absorbed, helping prevent dehydration, which improves appetite and energy.
Medications also play a role in managing CKD complications. Phosphate binders are prescribed when diet alone is insufficient to control phosphorus levels. They reduce phosphorus absorption from the intestines. Managing high blood pressure is important as it can further damage the kidneys; medications like amlodipine are commonly used to stabilize blood pressure.
Other medications address other issues from CKD. Anti-nausea drugs help alleviate gastrointestinal upset. For anemia, a common complication where kidneys produce less red blood cell hormone, treatments like molidustat (Varenzin-CA1) are available. Molidustat works by stimulating erythropoietin production, helping to increase red blood cell counts and improve energy.
Prognosis and Supporting Quality of Life
Chronic kidney disease is a progressive condition with no cure. However, with consistent and appropriate management, many cats can maintain a good quality of life for an extended period. Prognosis often depends on the diagnosis stage and treatment response. For example, Stage 2 cats might have an average survival time of two to three years, while Stage 4 cats generally have a prognosis of less than six months.
Factors that can influence a cat’s prognosis include protein loss in urine, elevated phosphorus levels, and anemia. Early detection and prompt management can significantly impact both the length and comfort of a cat’s life. Regular veterinary monitoring is important to assess disease progression and adjust therapies as needed.
Supporting a cat’s quality of life at home is important, even as the disease advances. Creating a comfortable environment includes providing warm and soft resting areas. Ensuring easy access to food, water, and litter boxes is also beneficial, especially for cats with muscle weakness or mobility challenges. Minimizing stress by maintaining a predictable daily routine and a calm household atmosphere contributes to their well-being.