Urolithiasis (urinary stone disease) affects both the kidneys (nephrolithiasis) and lower urinary tract (urolithiasis) of dogs. Different stone types — calcium oxalate, struvite, urate, cystine — have distinct causes, treatments, and welfare implications. Understanding stone type is essential for appropriate management.
Common Stone Types
Struvite (magnesium ammonium phosphate): Most common in dogs; frequently infection-induced (urease-producing bacteria — Staphylococcus, Proteus — produce ammonia causing supersaturation); can often be dissolved medically with urinary acidification and infection elimination.
Calcium oxalate: Second most common; cannot be dissolved medically; associated with hypercalcaemia, hypercalciuria; surgical or interventional removal required; Miniature Schnauzers, Lhasa Apsos, Bichon Frisé, Shih Tzus predisposed.
Urate: Associated with portosystemic shunts (purine metabolism disorder) or with Dalmatians (genetically impaired uric acid metabolism); medical dissolution with allopurinol where possible.
Cystine: Inherited tubular transport defect; certain breeds (Newfoundlands, Mastiffs, Labrador Retrievers); requires specific dietary modification and, if necessary, D-penicillamine therapy.
Clinical Signs
- Haematuria (blood in urine)
- Dysuria — straining to urinate, frequent urination of small volumes
- Pollakiuria — frequent urination
- Urethral obstruction — emergency requiring immediate intervention (particularly in male dogs)
- Renal pain in nephrolithiasis — reluctance to move, arched back
- Recurrent urinary tract infections
Diagnosis
Radiography identifies radiopaque stones (struvite, calcium oxalate, cystine); urate stones may be radiolucent requiring ultrasound. Urinalysis and culture identifies infection. Stone analysis after surgical removal, voiding, or retrieval by urohydropulsion guides long-term prevention.
Prevention and Long-Term Management
Increasing water intake is the most universally applicable prevention strategy — dilute urine reduces mineral supersaturation for all stone types. Prescription urinary diets formulated for specific stone types significantly reduce recurrence. Regular monitoring (urinalysis every 3–6 months, imaging annually) detects recurrence before clinical signs develop.