🩺 Vet Guide 2025: Chronic Kidney Disease in Dogs and Cats – Early Signs, Stages & Treatment 🐶🐱💧

By Dr Duncan Houston, BVSc

🔍 What Is Chronic Kidney Disease?

Chronic Kidney Disease (CKD), also referred to as renal insufficiency or chronic renal failure, is a gradual loss of kidney function over time. The kidneys do much more than make urine—they help regulate blood pressure, hydration, red blood cell production, blood pH, and calcium/phosphorus balance. 🧠💧

📉 How Kidney Function Declines

Each kidney contains millions of filtering units called nephrons. Dogs and cats are born with more than they need, but as pets age or experience damage from illness or toxins, nephrons die. Once too many are lost, the remaining kidney function becomes insufficient, leading to symptoms and complications.

🧪 Signs of Early Kidney Disease

• 💦 Increased thirst
• 🚽 Increased urination
• 🐌 Lethargy or reduced activity
• 🦴 Weight loss or poor appetite
• 🩸 Vomiting or bad breath (uremia)

📊 Kidney Function Testing

Veterinarians use blood and urine tests to assess kidney health:

• Creatinine – waste product from muscles, builds up when kidneys fail
• SDMA – detects kidney damage earlier than creatinine
• BUN (blood urea nitrogen) – reflects protein metabolism and kidney performance
• Urinalysis – checks concentration, protein, and infection signs
• UPC Ratio – determines protein loss in the urine
• Blood Pressure – high blood pressure can damage kidneys further

📈 IRIS Staging of Kidney Disease

The International Renal Interest Society (IRIS) provides guidelines for staging CKD in pets. Stages are based on creatinine and SDMA levels:

Dogs

• Stage I: Creatinine <1.4 mg/dL, SDMA <18
• Stage II: Creatinine 1.4–2.8, SDMA 18–35
• Stage III: Creatinine 2.9–5.0, SDMA 36–54
• Stage IV: Creatinine >5.0, SDMA >54

Cats

• Stage I: Creatinine <1.6 mg/dL, SDMA <18
• Stage II: Creatinine 1.6–2.8, SDMA 18–25
• Stage III: Creatinine 2.9–5.0, SDMA 26–38
• Stage IV: Creatinine >5.0, SDMA >38

Sub-Staging

• 📈 Blood pressure: normotensive or hypertensive
• 💧 Protein loss: proteinuric, borderline, or non-proteinuric

🧬 Kidney Function Roles & What Goes Wrong

💧 Water Conservation

Kidneys normally concentrate urine. When damaged, they cannot, leading to excessive water loss and thirst.

🧪 Toxin Removal

Kidneys filter waste from the bloodstream. As nephrons die, toxins build up (azotemia), and symptoms like vomiting or lethargy appear (uremia).

🦴 Calcium/Phosphorus Balance

When kidney function drops, phosphorus builds up and calcium balance is disturbed. This can lead to bone issues and tissue mineralization.

⚡ Electrolyte Balance

CKD often causes low potassium levels, especially in cats, contributing to weakness and poor appetite.

🧬 Red Blood Cell Production

Kidneys make erythropoietin, which signals the body to make red blood cells. CKD can cause anemia that may need injectable therapy.

🔬 pH Balance

Loss of pH control results in acid buildup (metabolic acidosis), which worsens symptoms. Fluid therapy often corrects this.

💊 Treatment by Stage

Stage I

• 🧪 Monitor blood pressure and urinary protein
• 📅 Recheck every 3 months

Stage II

• 🍽️ Begin renal diet
• 🧪 Monitor phosphorus, potassium, and blood pressure
• 📅 Recheck every 3 months

Stage III

• 💊 Manage nausea, acid-base imbalance
• 🩸 Monitor hematocrit for anemia
• 🌞 Consider vitamin D (calcitriol)

Stage IV

• 💉 Subcutaneous fluids at home
• 🥣 Ensure calorie intake; assisted feeding if needed
• 🔁 Frequent monitoring and supportive care

⚠️ Special Conditions

Pyelonephritis

Kidney infection caused by untreated bladder infections. May be reversible if detected early. Urine culture is critical for diagnosis.

Ureteral Stones

Stones in the ureter can block kidney drainage, damaging it. Imaging helps detect these quickly. Sudden creatinine spikes can be a clue.

🏁 Prognosis & Long-Term Outlook

CKD is progressive and incurable, but many pets live months to years with excellent quality of life through proper care. Monitoring and early detection are key.

📲 Concerned About Kidney Health? Ask A Vet Today

From early screening to home care plans, you don’t have to manage CKD alone. Download the Ask A Vet app to chat with Dr Duncan Houston and get tailored advice for your pet's kidney health 🩺🐶🐱.