A common concern for aging cats is chronic kidney disease (CKD), a progressive condition affecting kidney function. CKD can be challenging to manage, but early diagnosis and proper assessment can significantly improve the chance of slowing down the progression of this condition.
What is Chronic Kidney Disease (CKD)?
CKD refers to the long-term, irreversible deterioration of kidney function. The kidneys filter waste products from the blood and maintaining proper fluid balance. As kidney function declines, waste products accumulate, leading to various health issues. CKD is most common in older cats, with studies showing it affects 30–40% of cats over 10 years of age.
Routine Diagnosis of CKD
The first step in diagnosing CKD is recognizing the clinical signs, which may include:
- Weight loss
- Increased thirst (polydipsia)
- Increased urination (polyuria)
- Poor appetite
- Vomiting or nausea
- Lethargy
We recommend screening blood and urine tests for cats over ten years old, as early-stage CKD may not present with obvious symptoms.
CKD is typically diagnosed based on blood tests showing elevated levels of one or more kidney parameters (azotaemia) and/or a urine specific gravity (USG) test that indicates dilute urine.
Why Early Diagnosis is Important
Diagnosing CKD early is key to informing the way we manage this progressive disease. With proactive care, including dietary changes, hydration management, and medications, many cats with CKD can live for years with a good quality of life. Ongoing monitoring helps track disease progression and ensures that treatments are adjusted as needed.
What do We Check When Assessing Kidney Function in your Cat?
1. Full History and Physical Examination: We begin by gathering a thorough history of your cat’s health and any symptoms such as weight loss, increased thirst, or frequent urination. A physical exam will help assess kidney size, hydration levels, and other signs of CKD.
2. Routine Urinalysis: A urine test is essential for assessing kidney function. We will check for:
- Urine Specific Gravity (USG) to determine how well the kidneys are concentrating urine.
- Protein levels to detect proteinuria, which can indicate kidney damage.
- Sediment analysis to look for abnormal cells or crystals.
- Bacterial culture, if needed, to rule out urinary tract infections.
3. Serum Biochemistry: Blood tests will be conducted to measure important markers of kidney function:
- Creatinine, urea and SDMA levels are key indicators of how well the kidneys are filtering waste products from the blood.
- Electrolyte balance, including sodium, potassium, and phosphorus levels, helps assess the kidneys' ability to maintain normal body function.
- Thyroid hormone levels in older cats to rule out hyperthyroidism, a condition that can mask CKD symptoms.
4. Routine Haematology: A complete blood count helps detect anemia or other abnormalities. Many cats with CKD suffer from anemia due to reduced production of erythropoietin, a hormone produced by the kidneys that stimulates red blood cell production.
5.. Diagnostic Imaging: Ultrasound is used to examine the kidneys’ structure and identify potential abnormalities, such as stones or tumors. Ultrasound is particularly useful in assessing the size, shape, and internal structure of the kidneys.
Staging CKD in Cats
Once CKD is diagnosed, we use the IRIS staging system to classify the disease's severity. This system categorizes CKD into four stages based on blood creatinine levels:
- Stage 1: Non-azotemic, with subtle or no symptoms.
- Stage 2: Mild azotemia, with creatinine levels between 140–250 µmol/l.
- Stage 3: Moderate azotemia, with creatinine levels between 250–440 µmol/l, and more obvious clinical signs.
- Stage 4: Severe azotemia, with creatinine levels over 440 µmol/l, often leading to marked symptoms..
In addition to creatinine levels, other factors such as blood pressure, protein levels in urine, and the presence of other conditions are used to "sub-stage" CKD, helping veterinarians tailor the most appropriate treatment plan.
Urine Protein: Creatinine Ratio (UPCR): Measuring the amount of protein in the urine is important for sub-staging CKD. Excessive protein in the urine (proteinuria) is a sign of significant kidney damage and is associated with a poorer prognosis
Systolic Blood Pressure (SBP): High blood pressure (hypertension) is a common complication of CKD in cats. Measuring your cat’s blood pressure is crucial because untreated hypertension can cause further kidney damage and other health problems like blindness.
Below is a video of an elderly patient with CKD having her blood pressure assessed with a Doppler machine.
Learning that your cat has been diagnosed with kidney disease can be upsetting and daunting for many owners. We've put together a series of blog posts to help guide you through some key aspects of management to hopefully slow down the progression of CKD and maintain your cat's quality of life for as long as possible.
Take a moment to read our other blog posts about other important management aspects of CKD: