Chronic Kidney Disease

Chronic kidney disease (CKD) is the leading cause of death in cats > 10 years. It is progressive, irreversible nephron loss.

Clinical signs: weight loss, poor appetite, lethargy, PU/PD, vomiting, halitosis (uremia), pale mucous membranes.

Diagnosis requires:

• Azotemia (elevated BUN and/or creatinine)
• Inappropriately dilute urine (USG < 1.035 in azotemic cat)
• Evidence of chronicity (small kidneys, hyperplastic parathyroid, non-regenerative anemia)

SDMA: Rises earlier than creatinine when ~25% of nephrons are lost. May detect CKD before creatinine elevates.

Creatinine-based stages (fasted, hydrated):

• Stage 1: < 1.6 mg/dL (or SDMA elevated, creatinine normal)
• Stage 2: 1.6–2.8 mg/dL
• Stage 3: 2.9–5.0 mg/dL
• Stage 4: > 5.0 mg/dL

Proteinuria substaging (UPC):

• Non-proteinuric: < 0.2
• Borderline: 0.2–0.4
• Proteinuric: > 0.4 → treat with ACE inhibitor (benazepril)

Blood pressure substaging:

• Normotensive: < 150 mmHg
• Hypertensive: > 160 mmHg → treat with amlodipine

1. Renal diet:

• Restricted phosphorus (0.5–0.8% DM)
• Moderate protein restriction (not severe — maintain muscle mass)
• Increased omega-3 fatty acids
• Increased caloric density (cats eat less)

2. Phosphate binders: Aluminum hydroxide, calcium acetate, or lanthanum carbonate if diet alone insufficient.

3. ACE inhibitors: Benazepril 0.5–1.0 mg/kg PO daily if UPC > 0.4. Reduces proteinuria and slows progression.

4. Antihypertensives: Amlodipine 0.625–1.25 mg/cat PO daily if SBP > 160 mmHg.

5. Subcutaneous fluids: Lactated Ringer's 100–200 mL q24-48h for Stage 3–4 or dehydration.

6. Appetite stimulants: Mirtazapine 1.875–3.75 mg PO q48-72h or capromorelin.

7. Erythropoietin / darbepoetin: For refractory anemia (Hct < 20%).