Moderate severity

Bladder Stones (Urolithiasis)

Hard mineral stones that form in a cat's bladder, causing straining, bloody urine and — in male cats especially — the risk of a life-threatening blockage of the urethra.

⚠️ Common symptoms

Straining to urinate, often with little or nothing producedBlood in the urine (pink or red tinge)Frequent trips to the litter boxUrinating outside the box, in odd placesCrying or signs of pain while urinatingExcessive licking of the genital areaA hard, painful belly and, in a full blockage, lethargy, vomiting and collapse

Bladder stones — known medically as urolithiasis — are one of the more common and more serious problems affecting a cat's lower urinary tract. They begin as microscopic crystals in urine that is too concentrated or has drifted to a pH that encourages minerals to fall out of solution. Over time those crystals aggregate into solid stones, called uroliths, that can range from a gritty sand to stones the size of a marble. The two dominant types in cats are struvite and calcium oxalate, and telling them apart matters enormously because it decides whether the stones can be dissolved or must be removed.

The signs of stones come from the irritation and obstruction they cause. Rubbing against the bladder wall, they trigger inflammation, so a cat strains, passes bloody urine, visits the litter box again and again, and often begins urinating in unusual places. Many owners first mistake this for a behavioural problem or a simple infection. In female cats the wide urethra usually lets stones and grit pass, but in male cats the urethra narrows to a fine point, and a stone or a plug of crystals and mucus can lodge there and block the flow of urine completely. This is a medical emergency: with nowhere to go, toxins and potassium build up in the blood within hours, the bladder can rupture, and an untreated cat may die in a day or two.

Diagnosis usually involves a urine test to look at crystals, pH and infection, plus X-rays or ultrasound to see the stones directly. From there, treatment splits along type. Struvite stones are the good-news category: a therapeutic diet that acidifies the urine and limits the minerals involved can dissolve them over four to twelve weeks, sparing the cat surgery. Calcium oxalate and most other stones will not dissolve and are removed surgically, most often by opening the bladder in an operation called a cystotomy, with the stones sent to a laboratory to confirm their make-up.

Because stones love to return, the real work is preventive and lifelong. It centres on one simple idea — dilute the urine. A cat that eats wet food and drinks plenty produces more, weaker urine that flushes crystals away before they can gather. Prescription urinary diets, weight control, plenty of clean litter boxes and regular urine checks round out a plan that keeps most stone-prone cats comfortable and out of the operating theatre.

🔍 Causes

Bladder stones form when minerals dissolved in the urine become over-concentrated and crystallise, then clump together into stones. The two commonest types in cats are struvite (magnesium ammonium phosphate) and calcium oxalate. Contributing factors include urine that is too concentrated because a cat drinks too little, urine pH that favours one crystal type, diet, some urinary infections, and individual metabolic quirks. Overweight, inactive, middle-aged indoor cats on dry-only diets are especially prone, and some breeds show a higher tendency to oxalate stones.

🛡 Prevention

The single most powerful preventive is keeping the urine dilute — which means getting more water into your cat. Feeding wet food, adding water to meals, and encouraging drinking with fountains and multiple water stations all help. Cats prone to stones are usually kept on a veterinary urinary diet formulated to keep the urine at a stone-unfriendly pH and mineral balance. Maintaining a healthy weight, providing plenty of clean litter boxes to encourage regular urination, and having recurrent cases monitored with periodic urine tests all reduce the chance of stones returning.

💊 Treatment

Treatment depends on the type of stone. Struvite stones can often be dissolved over several weeks with a special therapeutic diet that changes the urine's acidity, avoiding surgery altogether. Calcium oxalate and other stones cannot be dissolved and usually must be removed — most commonly by an operation to open the bladder (cystotomy), or sometimes by less invasive techniques that flush or extract small stones. A male cat with a complete urethral blockage is an emergency: the vet must pass a catheter under sedation to relieve it and treat the resulting toxin and potassium build-up. Long-term, a prescription diet and plenty of water intake are used to stop stones re-forming.

When to see a vet: Any cat straining in the litter box needs to be seen promptly, and a male cat that is straining but producing little or no urine is a true emergency — a blocked urethra can cause kidney failure and death within a day or two, so seek care immediately, day or night. Book a same-day appointment for blood in the urine, repeated unproductive squatting, crying while urinating, or urinating outside the box, since these signs also overlap with painful cystitis and infections that need diagnosis.

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⚕️ Medical disclaimer

  • This information is educational only and is not a substitute for veterinary advice.
  • Symptoms overlap between conditions — only a vet can diagnose accurately.
  • Never withhold treatment or self-medicate based on information found online.
  • When in doubt, call your vet. Early intervention almost always leads to better outcomes.

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