Bladder Stones (Urolithiasis)

Bladder stones (uroliths) form when minerals in the urine crystallise and aggregate into stones that accumulate in the bladder. The most common types in dogs are struvite (magnesium ammonium phosphate) and calcium oxalate. Less common types include urate (especially in Dalmatians and dogs with liver disease), cystine, and silicate.

Stone type matters because treatment and prevention differ significantly between types. A stone visible on X-ray or ultrasound must be analysed - either by dissolving it (if possible) or by surgical removal followed by stone analysis - before an appropriate prevention strategy can be implemented.

Signs to monitor

Bladder stones cause similar signs to UTIs:

• Frequent urination, often in small amounts
• Straining or pain when urinating
• Blood in urine
• Licking at the genitalia
• Accidents indoors in a house-trained dog

Signs that suggest a stone has moved into the urethra and caused an obstruction (an emergency):

• Straining repeatedly with no urine output
• Crying in pain
• Lethargy
• Distended, painful abdomen

A urethral obstruction - particularly in male dogs, whose urethra is narrower - is a life-threatening emergency requiring immediate veterinary care.

Diagnosis

Bladder stones are diagnosed by:

• X-ray: Struvite and calcium oxalate stones are radiodense (visible on plain X-rays). Urate and cystine stones may be radiolucent (invisible on plain X-ray - ultrasound needed).
• Ultrasound: Identifies all stone types; also assesses the bladder wall, kidneys, and whether any stones are present in the kidney (nephroliths).
• Urine analysis: Crystal type in urine suggests stone composition, though is not definitive.

Stone analysis requires either surgical removal or dissolution - the actual stone composition can only be confirmed by laboratory analysis of retrieved stone material.

Treatment

Struvite stones: Often dissolve with a prescription struvite dissolution diet (low in protein, magnesium, and phosphate; produces acidic urine) combined with treating any associated UTI. This takes 4–12 weeks. Follow-up imaging confirms dissolution.

Calcium oxalate stones: Do not dissolve with diet - surgical removal (cystotomy) or less invasive procedures (voiding hydropulsion for small stones, cystoscopic removal) are required.

Urate stones: In Dalmatians, a low purine diet and allopurinol reduce uric acid excretion and prevent recurrence. In other breeds, urate stones often indicate underlying liver disease (portosystemic shunt) that needs addressing.

All types: Increased water intake is universally helpful - diluted urine reduces mineral saturation. Wet food, water added to food, or multiple water bowls encourages higher intake.

Prevention and dietary management

After treatment, long-term prevention requires a diet appropriate for the stone type:

• Struvite prevention: Maintain urine acidity; avoid excessive dietary magnesium; ensure any UTIs are treated promptly (struvite stones often form around bacterial infection)
• Calcium oxalate prevention: Moderate restriction of dietary calcium and oxalate; increased hydration; avoid excess vitamin C supplementation
• Urate prevention: Low-purine diet; allopurinol if appropriate

Log dietary compliance and water intake. Monitor with urinalysis every 3–6 months to check urine pH and crystal content.

Repeat imaging

Dogs who have had bladder stones have a significant recurrence risk. Follow-up abdominal imaging (ultrasound or X-ray) is recommended:

• 3 months after struvite dissolution to confirm complete resolution
• Every 6–12 months to detect recurrence before stones become symptomatic

Log each imaging date and the findings.

When to contact your vet

Go to the emergency vet immediately if:

• Straining to urinate with no output
• Severe pain, collapse, or distended abdomen

Contact your vet soon if:

• Signs of UTI or haematuria
• Current dietary prevention isn't achieving target urine parameters

Schedule routine monitoring for:

• Follow-up urinalysis
• Imaging to detect recurrence

Frequently Asked Questions

Do bladder stones always need surgery? Not always. Struvite stones can often be dissolved with prescription diet. Small stones may be flushed out under sedation (voiding hydropulsion). Calcium oxalate stones require surgical removal. The appropriate approach depends on stone type and size.

Can I feed my dog a regular diet if they've had bladder stones? Not without vet advice. Recurrence rates are high without appropriate dietary management. The specific diet required depends on stone type, so stone analysis after treatment is necessary before choosing a prevention diet.

My dog had bladder stones removed - does that mean they're cured? Stone removal treats the immediate problem but not the underlying predisposition. Without dietary management and monitoring, recurrence is common - in some breeds and stone types, the recurrence rate without intervention is over 50%.

Why is water intake important? Diluted urine reduces mineral concentration and makes it harder for crystals to form. Increasing water intake is one of the most effective preventive measures regardless of stone type. Wet food significantly increases daily water intake compared to dry food.

Are certain breeds always at risk? Some breeds have specific genetic predispositions: Dalmatians have impaired uric acid metabolism and are prone to urate stones throughout their lives. Miniature Schnauzers have a particularly high predisposition to calcium oxalate and struvite stones. For these breeds, regular urinalysis from middle age is prudent even without symptoms.