🔍 What is Calcium Phosphate Urolithiasis?

Calcium phosphate uroliths—often composed of hydroxyapatite, brushite, whitlockite, or octacalcium phosphate—are uncommon in cats, typically forming in the kidneys rather than the bladder :contentReference[oaicite:4]{index=4}. Also called apatite stones, they differ from more common struvite and calcium oxalate uroliths.

1. Causes & Risk Factors

• Hypercalcemia is a major trigger—secondary to hyperparathyroidism, idiopathic hypercalcemia, or neoplasia :contentReference[oaicite:5]{index=5}.
• Other associated conditions include parathyroid hormone excess, metastatic or dystrophic mineralization, and certain metabolic disorders :contentReference[oaicite:6]{index=6}.
• Dietary imbalances with excess calcium or phosphorus, or systemic illnesses (like chronic kidney disease), can contribute :contentReference[oaicite:7]{index=7}.

2. Who is Affected?

• Typically older cats, especially those with documented hypercalcemia or kidney issues :contentReference[oaicite:8]{index=8}.
• No strong breed or sex predilection noted, but cats with metabolic disturbances should be monitored closely.
• Compared to struvite or oxalate stones, calcium phosphate stones remain rare in feline patients :contentReference[oaicite:9]{index=9}.

3. Symptoms & Clinical Signs

• Often asymptomatic in early stages. Stones in kidneys may be incidental findings :contentReference[oaicite:10]{index=10}.
• When symptomatic, cats may exhibit polyuria, hematuria, dysuria, straining, or cloudy urine :contentReference[oaicite:11]{index=11}.
• Chronic kidney stones may cause intermittent pain, poor appetite, weight loss, vomiting, or decreased kidney function.
• Obstructive cases may present with acute signs—distended bladder, anuria, collapse, or azotemia.

4. Diagnostic Approach

1. History & exam: assess hydration, pain, and kidney function.
2. Bloodwork: CBC, chemistry panel with calcium, phosphorus, kidney values; check ionized calcium :contentReference[oaicite:12]{index=12}.
3. Urinalysis: note crystals, specific gravity, pH, infection.
4. Imaging: radiographs detect radiopaque stones; ultrasound confirms location, size, hydronephrosis; stones appear as hyperechoic with acoustic shadowing :contentReference[oaicite:13]{index=13}.
5. Stone analysis: essential post-removal to confirm composition and guide therapy.

5. Treatment Options

a. Medical / Metabolic Management

• Address underlying hypercalcemia through diet modification, parathyroidectomy, or medication.
• Hydrochlorothiazide can reduce urine calcium excretion in recurrent cases :contentReference[oaicite:14]{index=14}.
• Maintain moderate urine pH and promote hydration to prevent new crystal formation :contentReference[oaicite:15]{index=15}.

b. Surgical or Interventional Removal

• Nephrolithotomy or ureteral surgery if obstructive.
• Bladder stones may require cystotomy for removal.

c. Non-Surgical Techniques

• Voiding urohydropropulsion or retrieval devices may work for small stones, especially in bladders of female cats :contentReference[oaicite:16]{index=16}.
• Lithotripsy may be considered in select cases but is rare in cats.

6. Prognosis & Follow-up

• Stone-free prognosis is good if hypercalcemia and diet are corrected.
• Recurrence possible if underlying imbalance persists.
• Periodic rechecks (every 3–6 months) with bloodwork and imaging are recommended :contentReference[oaicite:17]{index=17}.
• If CKD is present, monitor kidney function closely during management.

7. Prevention Strategies

• Optimize diet with balanced calcium-phosphorus ratios; avoid supplementation unless prescribed :contentReference[oaicite:18]{index=18}.
• Encourage water intake—wet food and fountains to dilute urine.
• Maintain neutral urine pH (~6.6–7.5) to minimize stone formation :contentReference[oaicite:19]{index=19}.
• Treat and monitor metabolic disease (e.g., hyperparathyroidism, CKD).

8. Ask A Vet Remote Monitoring 🐾📲

• 📸 Upload ultrasound or x‑ray reports for specialist review.
• 🔔 Medication reminders—diuretics, metabolic therapies, pain relief.
• 🧭 Track drinking, urination, appetite, and body weight.
• 📊 Alerts if urine changes—straining, blood, reduced output, or altered behavior.
• 👥 Virtual follow‑ups help coordinate imaging schedules and adjust protocols.

9. FAQs

Can calcium phosphate stones be dissolved?

No—like calcium oxalate, they require removal; no effective dissolution exists :contentReference[oaicite:20]{index=20}.

Why are they rare?

They form under specific metabolic conditions—uncommon in cats—compared to oxalate or struvite stones :contentReference[oaicite:21]{index=21}.

What follow-up is needed after removal?

Reassess blood calcium, kidney health, and perform imaging every 3–6 months.

10. Take‑Home Tips ✅

• Recognize risk: any hypercalcemic cat with urinary signs needs evaluation.
• Diagnose early: use blood and imaging to catch stones before complications.
• Select treatment wisely: address metabolic issues and remove obstructive stones.
• Prevent recurrence: through nutrition, hydration, and metabolic control.
• Rely on Ask A Vet: for medication reminders, monitoring, and remote vet support.

Conclusion

While calcium phosphate urolithiasis is rare in cats, early identification and metabolic control are key to preventing recurrence. With tailored treatment, surgical management of obstructive stones, and diligent follow-up, cats can enjoy healthy kidney function and a stone-free life. Ask A Vet’s remote monitoring—image review, symptom logs, medication alerts—ensures seamless collaboration between pet parents and veterinarians in 2025 and beyond 🐾📲.

If your cat shows signs of frequent urination, hematuria, or bloodwork reveals hypercalcemia—schedule a veterinary exam promptly and start Ask A Vet monitoring for enhanced care coordination and peace of mind.