Struvite Bladder Stones in Cats: Symptoms, Treatment and Prevention

By Dr Duncan Houston

Struvite bladder stones can cause blood in the urine, painful urination and repeated litter-tray visits. In male cats, a stone or associated inflammatory material may enter the narrow urethra and cause a life-threatening urinary blockage.

The good news is that suspected struvite stones are often treatable without surgery. A correctly selected veterinary dissolution diet can gradually dissolve them inside the bladder.

The important part is confirming that dissolution is appropriate. Crystals do not prove that a cat has stones, and an X-ray cannot identify every stone type with certainty. The cat still needs a proper urinary investigation and repeat imaging to confirm that the stones are shrinking.

Quick Answer

Struvite stones are urinary stones made primarily from magnesium, ammonium and phosphate. They commonly form in the bladder and are usually visible on radiographs.

When struvite is considered the most likely mineral and the cat is not obstructed, a veterinary dissolution diet is generally the preferred first treatment. The diet must be fed exclusively, and repeat radiographs are usually performed every two to three weeks until the stones have disappeared.

Struvite Stones at a Glance

Question	Practical answer
What are struvite stones made from?	Magnesium ammonium phosphate
Are struvite crystals and stones the same?	No. Crystals may occur without stones
Are most feline struvite stones infected?	Many are sterile, but infection-induced stones do occur
Can they be dissolved?	Yes, when the mineral prediction is correct
How long does dissolution take?	Commonly 14 to 21 days, but sometimes up to 56 days
Must the diet be fed exclusively?	Yes, except for treats specifically confirmed as compatible
Can dry dissolution food work?	Yes. Both dry and canned therapeutic diets can be effective
How are stones monitored?	Usually with radiographs every two to three weeks
What if the stones do not shrink?	Recheck compliance, urinalysis, urine culture and the predicted mineral type
Are antibiotics always needed?	No. Only when clinically significant infection is identified
Can male cats undergo dissolution?	Yes, when they are not obstructed and can be monitored appropriately
When is it an emergency?	Repeated straining with little or no urine, especially in a male cat

Struvite and calcium oxalate together account for approximately 90% to 95% of feline lower urinary tract stones. Unlike struvite, calcium oxalate cannot be dissolved medically.

What Are Struvite Bladder Stones?

Struvite is a crystalline mineral composed of:

• Magnesium

• Ammonium

• Phosphate

Struvite stones may also be described as magnesium ammonium phosphate stones. “Triple phosphate” is an older term sometimes used for the same mineral.

These minerals are naturally present in urine. A stone develops when the urine becomes sufficiently supersaturated for microscopic crystals to form, remain within the urinary tract and gradually aggregate around organic material.

A struvite stone may contain:

• Mineral crystals

• Mucus

• Proteins

• Blood cells

• Inflammatory debris

• Bacterial material when infection is present

Individual stones may be small and numerous or larger and solitary. Most feline struvite bladder stones are radiopaque, meaning they can generally be seen on standard radiographs.

Are Struvite Crystals the Same as Struvite Stones?

No.

Crystalluria means crystals were detected in a urine sample. Urolithiasis means an organised physical stone has formed within the urinary tract.

A cat can have struvite crystals without having a bladder stone. Crystals may also appear because:

• The urine is concentrated

• The urine is alkaline

• The sample was refrigerated

• Analysis was delayed

• The urine changed after leaving the body

• The cat recently ate

• The cat is consuming a diet that affects urine composition

A cat can also have a struvite stone without detectable crystals in the sample examined that day.

This is why crystals should never be used as the sole basis for diagnosing a stone or prescribing a dissolution diet. Imaging is needed to confirm whether physical stones are present.

Why Do Struvite Stones Form?

Stone formation depends on several interacting factors rather than one ingredient or one abnormal urine result.

Important contributors include:

• Concentrated urine

• High urinary concentrations of mineral precursors

• Urine pH

• Diet

• Water intake

• Individual metabolism

• Genetics

• Urinary infection in selected cats

• Other concurrent diseases

Struvite becomes less soluble as urine conditions favour crystallisation. Therapeutic dissolution diets work by producing urine that is undersaturated with struvite, reducing magnesium and phosphorus availability, controlling urine acidity and often increasing urine volume.

Does Alkaline Urine Cause Struvite Stones?

Alkaline urine can favour struvite precipitation, but one alkaline urine sample does not prove that a stone is present.

Urine pH changes throughout the day and may be affected by meals, diet, infection and sample handling. The veterinarian interprets pH alongside:

• Urine concentration

• Sediment examination

• Bacterial culture

• Radiographs

• Stone size and appearance

• The cat’s age and medical history

Trying to acidify urine aggressively without knowing the mineral type is unsafe. Excessive urinary acidification may increase the risk of calcium oxalate stones, which cannot be dissolved.

Are Feline Struvite Stones Caused by Infection?

Many feline struvite stones form in sterile urine, particularly in younger and otherwise healthy cats. This differs from dogs, where infection-induced struvite is much more common.

However, infection-induced struvite does occur in cats. The likelihood becomes more important in:

• Older cats

• Cats with diabetes

• Cats with chronic kidney disease

• Cats with previous urinary catheterisation

• Cats with a perineal urethrostomy

• Cats with recurrent urinary infections

• Cats with anatomical urinary abnormalities

• Cats receiving immunosuppressive medication

• Cats with unusually large or rapidly growing struvite stones

A 2026 surgical-case study found urease-producing bacteriuria in 43% of cats with confirmed struvite stones, although the authors cautioned that the selected surgical population may have overrepresented infected or dissolution-resistant cases. The old statement that approximately 95% of feline struvite stones are sterile is therefore too absolute for every patient.

When infection is suspected, urine should ideally be collected directly from the bladder for culture before antibiotics begin.

What Are the Signs of Struvite Bladder Stones?

Common signs include:

• Blood in the urine

• Straining to urinate

• Pain or vocalisation while urinating

• Frequent passage of small amounts of urine

• Urinating outside the litter tray

• Excessive genital licking

• Restlessness

• Hiding

• Reduced appetite

• Irritability when the abdomen is touched

Some cats have stones detected incidentally during imaging for another reason and show no obvious urinary signs.

The symptoms do not reveal the mineral type. Feline idiopathic cystitis, bacterial infection, calcium oxalate stones, tumours and urethral obstruction can all look similar.

How Worried Should You Be?

Lower Immediate Risk

Your cat has:

• Mildly increased urinary frequency

• A small amount of blood

• Normal-sized urine clumps

• Normal appetite

• Normal energy

• No persistent straining

What it may mean: A non-obstructive lower urinary tract disease is possible.

What to do: Arrange veterinary assessment within 24 hours. Stones, cystitis and infection cannot be distinguished reliably at home.

Moderate Concern

Your cat has:

• Repeated litter-tray visits

• Painful urination

• Smaller urine clumps

• Blood in the urine

• Genital licking

• Urination outside the tray

• Reduced appetite

What it may mean: Bladder stones, feline idiopathic cystitis, infection or partial obstruction may be present.

What to do: Seek same-day veterinary care. A male cat producing only tiny amounts should be treated as potentially obstructed.

High Concern

Your cat has:

• Persistent straining

• Only repeated drops of urine

• No normal urine stream or clump

• A painful or enlarged abdomen

• Vomiting

• Food refusal

• Marked lethargy

• Weakness

What it may mean: Urethral obstruction is likely or must be ruled out immediately.

What to do: Attend an emergency veterinary hospital now.

Critical

Your cat has:

• Collapse

• Inability to stand

• Profound weakness

• Low body temperature

• An abnormal or slow heartbeat

• Laboured breathing

• Minimal responsiveness

What it may mean: Severe hyperkalaemia, acute kidney injury, shock or bladder rupture may be occurring.

What to do: Immediate emergency stabilisation is required.

When Is This an Emergency?

A male cat repeatedly straining while producing little or no normal urine is experiencing an emergency until proven otherwise.

A stone, urethral plug or inflammatory material may block the narrow male urethra. Pressure then builds within the bladder while potassium, acids and waste products accumulate in the blood.

Seek immediate veterinary care if your cat:

• Produces no normal urine

• Produces only repeated drops

• Strains continuously

• Cries while attempting to urinate

• Vomits

• Stops eating

• Becomes markedly lethargic

• Has a painful or enlarged abdomen

• Becomes weak

• Feels unusually cold

• Collapses

• Appears confused or poorly responsive

Do not wait to see whether a urinary diet begins working. Dissolution is a treatment for stable bladder stones, not for an actively blocked urethra.

What Else Can Look Like Struvite Stones?

Possible condition	Why it matters
Feline idiopathic cystitis	The most common cause of lower urinary tract signs
Calcium oxalate stones	Cannot be dissolved with a struvite diet
Bacterial urinary infection	Requires appropriate urine culture and targeted treatment
Urethral plug	May cause partial or complete obstruction
Urethral stone	May become lodged and require urgent removal
Bladder tumour	More concerning in older cats with persistent blood
Blood clot	May irritate or obstruct the urinary tract
Urinary trauma	Can cause pain, haematuria and urine leakage
Urethral stricture	May follow previous obstruction or catheterisation
Constipation or colitis	Straining may be mistaken for urinary difficulty
Urine marking	Behavioural spraying differs from painful urination, but disease must be excluded first

The underlying problem may also change over time. A cat that previously formed struvite stones may later develop calcium oxalate stones, infection or feline idiopathic cystitis.

How Are Struvite Stones Diagnosed?

Physical Examination

The veterinarian assesses:

• Bladder size

• Bladder pain

• Hydration

• Temperature

• Heart rate

• Abdominal discomfort

• Evidence of urethral obstruction

• Kidney size

• Other signs of systemic disease

A very large, firm and painful bladder in a straining male cat substantially increases concern for obstruction.

Urinalysis

Urinalysis may provide information about:

• Urine concentration

• pH

• Blood

• Protein

• White blood cells

• Bacteria

• Crystal type

• Glucose

• Abnormal cells

Urinalysis supports mineral prediction but cannot confirm the stone’s composition by itself.

Urine Culture

Culture is particularly important when the cat:

• Is older

• Has recurrent urinary infections

• Has a perineal urethrostomy

• Has diabetes or kidney disease

• Has previously been catheterised

• Has bacteria or inflammatory cells on urinalysis

• Fails to respond as expected to dissolution

An infection-induced struvite stone will not dissolve reliably unless the infection is controlled with an appropriate antibiotic.

Radiographs

Most struvite and calcium oxalate stones are visible on standard radiographs.

Radiographs help determine:

• Whether stones are present

• Number of stones

• Approximate size

• Location

• Change during dissolution

• Whether urethral stones are present

Radiographic appearance may help predict composition. Struvite stones tend to be somewhat larger, less radiopaque and more irregular or heterogeneous than calcium oxalate stones, but there is substantial overlap. Definitive identification still requires laboratory analysis of a retrieved stone.

Ultrasound

Ultrasound can identify:

• Bladder stones

• Debris

• Blood clots

• Bladder-wall changes

• Masses

• Kidney and ureter abnormalities

However, ultrasound may overestimate stone size and underestimate the number of stones. It also cannot fully assess the intrapelvic and penile urethra. Standard radiographs are therefore particularly useful when planning dissolution or removal.

Can Struvite Bladder Stones Be Dissolved With Food?

Yes.

When struvite is considered the most likely mineral and there is no urgent reason for removal, medical dissolution should generally be attempted before surgery.

A veterinary dissolution diet alters the urine so that struvite is no longer stable. Minerals gradually leave the stone and return to solution, causing the stone to become:

• Smaller

• Less dense

• Less radiopaque

• Fewer in number

• Eventually absent on radiographs

Dissolution is not simply “feeding wet food” or selecting a supermarket product labelled for urinary health. It requires a therapeutic diet formulated and tested specifically for stone dissolution.

How Long Does Dissolution Take?

Current AAFP guidance reports that feline struvite dissolution generally takes approximately 14 to 21 days. Some stones dissolve more rapidly, while selected cases may require up to 56 days.

The time depends on:

• Stone size

• Number of stones

• Diet consumed

• Whether the diet is fed exclusively

• Water intake

• Infection

• Individual urine chemistry

• Whether the mineral prediction is correct

Improvement in urinary signs does not prove that the stones have disappeared. Repeat imaging is required.

Must the Cat Eat Only the Dissolution Diet?

Yes.

The diet should normally provide essentially all of the cat’s calories during dissolution. Other food can alter:

• Urine pH

• Magnesium intake

• Phosphorus intake

• Urine concentration

• Relative mineral saturation

Do not add:

• Ordinary treats

• Table food

• Other cat food

• Supplements

• Broths with unknown mineral or salt content

• Urinary acidifiers

Compatible treats may sometimes be permitted, but they should be specifically confirmed by the prescribing veterinarian or diet manufacturer.

In a multi-cat household, the cat undergoing dissolution may need:

• Separate feeding

• Microchip feeders

• Supervised meals

• Indoor confinement

• Removal of shared grazing bowls

In one prospective study, cats were required to consume the study diet exclusively, and no other treats, supplements or foods were permitted.

Does the Diet Have To Be Wet?

No.

Both canned and dry therapeutic dissolution diets can dissolve feline struvite stones when properly formulated and fed exclusively.

Canned food may still be preferred when the cat accepts it because its higher moisture content can:

• Increase total water intake

• Produce more dilute urine

• Increase urine volume

• Encourage more frequent bladder emptying

The best diet is one that is clinically appropriate and that the cat will consume reliably. A cat that refuses to eat must not be allowed to starve in an attempt to force acceptance of a new food.

How Is Dissolution Monitored?

The Minnesota Urolith Center recommends radiographs every two to three weeks during feline struvite dissolution.

Effective dissolution is demonstrated by a reduction in:

• Stone size

• Stone density

• Stone number

• Overall radiopacity

Urinalysis and urine culture may also be repeated, particularly when infection is possible.

What if the Stones Are Not Shrinking?

If no meaningful change is seen, the veterinary team should consider:

1. Is the cat eating the diet exclusively?

2. Is another cat’s food accessible?

3. Are treats or supplements being given?

4. Is a bacterial infection present?

5. Is the stone actually calcium oxalate or another mineral?

6. Is it a compound stone with more than one mineral?

7. Has the urine response been adequate?

8. Is another removal strategy now more appropriate?

No change or increasing stone size is a reason to reassess the plan rather than continuing the same diet indefinitely.

When Is Dietary Dissolution Not Appropriate?

Immediate or alternative treatment may be required when:

• The cat is urethrally obstructed

• A urethral stone cannot be returned to the bladder

• The cat cannot or will not eat the therapeutic diet

• The stone is unlikely to be struvite

• The stone is causing severe persistent pain

• The stone is associated with uncontrolled infection

• The bladder is at risk of damage

• The stone is not shrinking during a properly conducted trial

• Another concurrent disease makes the diet unsuitable

• Faster removal is medically necessary

The risk of obstruction during properly monitored dissolution of bladder struvite stones is considered very low, even in male cats. However, any male undergoing dissolution still needs close observation for repeated straining or reduced urine output.

What Other Treatments Can Remove Bladder Stones?

Voiding Urohydropropulsion

This technique uses a full bladder and controlled positioning to flush very small stones out through the urethra under anaesthesia.

It is generally limited to female cats with smooth stones smaller than approximately 2.5 mm. It is not recommended for intact male cats because their urethra is too narrow and obstruction may occur.

Cystoscopic Basket Retrieval

A small camera and retrieval basket are passed through the urethra.

This may be suitable for female cats with a limited number of stones smaller than approximately 3 mm. The normal male feline urethra is too small for routine retrograde cystoscopic retrieval.

Intracorporeal Lithotripsy

Lithotripsy uses specialised energy, commonly laser energy, to fragment stones so they can be removed through a cystoscope.

It is most practical in female cats with a relatively low stone burden and requires specialised equipment and expertise.

Percutaneous Cystolithotomy

A small incision allows an endoscope to enter the bladder directly.

Percutaneous cystolithotomy may be used in male or female cats and allows excellent visualisation and removal of stones without a full open cystotomy. It is generally performed by a trained referral team.

Surgical Cystotomy

During a cystotomy, the abdomen and bladder are opened surgically and the stones are removed.

Cystotomy may be appropriate when:

• Dissolution is unsuccessful

• Minimally invasive treatment is unavailable

• The stone burden is large

• Another bladder abnormality requires surgery

• Rapid removal is needed

• The stone type cannot be dissolved

Every removed stone should be submitted for quantitative mineral analysis. Appearance alone cannot reliably identify its composition.

Current feline guidance recommends considering dissolution first, followed by minimally invasive removal where appropriate, before moving to open cystotomy.

Are Antibiotics Needed?

Not routinely.

Antibiotics do not dissolve sterile struvite stones and should not be prescribed solely because crystals or stones are present.

They are appropriate when:

• A clinically significant urinary infection is confirmed

• Infection-induced struvite is suspected strongly

• Culture identifies a susceptible organism

• The cat has additional infection risk factors

When infection-induced struvite is present, the infection must be controlled throughout dissolution. Repeat urine cultures may be needed to confirm that bacteria have been eliminated.

What To Do Right Now

1. Confirm That Your Cat Is Passing Urine

Watch for:

• A normal stream

• Normal-sized urine clumps

• Repeated drops

• Blood

• Painful straining

A male cat producing only drops or no normal urine needs emergency examination.

2. Arrange Veterinary Imaging

Do not diagnose bladder stones from urinary signs or crystals alone.

Radiographs and, where appropriate, ultrasound are needed.

3. Ask Whether Struvite Is the Most Likely Mineral

The prediction should consider:

• Radiographic appearance

• Stone size and number

• Urine pH

• Crystal type

• Urine culture

• Age

• Medical history

• Concurrent disease

4. Feed the Prescribed Diet Exactly

Confirm:

• The precise food

• Whether canned, dry or both can be used

• Which treats are compatible

• How much to feed

• Whether other household cats can eat it

• When the first recheck is due

5. Record Urinary Signs

Monitor:

• Frequency of urination

• Urine-clump size

• Blood

• Straining

• Appetite

• Vomiting

• Energy

• Food compliance

6. Attend Every Imaging Recheck

Symptoms may improve before the stone has dissolved completely.

7. Do Not Add an Acidifier

Urinary acidifiers should not be combined casually with a properly formulated therapeutic diet. Excessive acidification can create additional mineral risk and may be dangerous for cats with particular medical conditions.

What Is the Prognosis?

The prognosis for sterile struvite bladder stones is generally excellent when:

• The mineral prediction is correct

• The cat eats the therapeutic diet exclusively

• Obstruction does not occur

• Infection is identified and treated when present

• Repeat imaging confirms progressive dissolution

• A long-term prevention plan is followed

Many stones dissolve within two to three weeks. Cats whose stones take longer should still show progressive reduction at each recheck.

Failure to dissolve does not automatically mean the diet is ineffective. The more common possibilities are dietary non-compliance, incorrect mineral prediction, infection or a mixed stone.

How Can Struvite Stones Be Prevented From Returning?

Use an Appropriate Maintenance Urinary Diet

After dissolution, the veterinarian may recommend a therapeutic maintenance food formulated to reduce struvite supersaturation.

Some dissolution diets are suitable for long-term adult maintenance, while others have specific indications or limitations. The decision should consider all of the cat’s health needs.

Increase Water Intake

Useful strategies include:

• Feeding canned food

• Adding water to food when accepted

• Providing several water bowls

• Trying different bowl shapes and materials

• Keeping water fresh

• Placing water away from food and litter

• Offering a fountain if the cat prefers moving water

Increasing dietary moisture helps reduce urine concentration and the saturation of minerals that form stones.

Treat Urinary Infection Properly

Cats with infection-induced struvite require:

• Culture-guided antibiotics

• Completion of the prescribed treatment

• Repeat urine culture

• Management of the factor allowing infection to recur

Maintain a Healthy Body Weight

Use:

• Measured meals

• Regular weighing

• Daily play

• Puzzle feeding

• Gradual veterinary-supervised weight loss when needed

Improve Litter-Tray Access

Provide:

• One tray per cat, plus one extra

• Large trays

• Quiet locations

• Easy access

• The cat’s preferred unscented litter

• Daily scooping

• More than one toileting location

Frequent comfortable urination helps prevent prolonged urine retention and allows owners to recognise changes earlier.

Continue Monitoring

The Minnesota Urolith Center recommends repeat urinalysis approximately every six months and urinary imaging annually after feline struvite stones, although individual cats may need closer surveillance. Cats with infection-induced stones may require urine culture every three to six months.

Common Struvite Stone Mistakes

Assuming Crystals Prove That Stones Are Present

Crystals and stones are related but not interchangeable.

Assuming Every Radiopaque Stone Is Struvite

Calcium oxalate is also radiopaque and cannot be dissolved.

Feeding the Dissolution Diet With Other Food

Even small additions may alter the therapeutic urine response.

Stopping the Diet When Symptoms Improve

Pain and blood may resolve before the stones disappear.

Skipping Repeat Radiographs

Imaging is needed to prove that dissolution is progressing.

Giving Antibiotics Without a Culture

Many feline struvite stones are sterile.

Adding Urinary Acidifiers to a Therapeutic Diet

Excessive acidification may increase calcium oxalate risk.

Using a Generic “Urinary” Food

Not every urinary food has a validated struvite-dissolution claim.

Failing To Analyse Removed Stones

Laboratory analysis is essential for accurate long-term prevention.

Waiting When a Male Cat Is Straining

A bladder stone or associated inflammatory material may cause urethral obstruction.

Frequently Asked Questions

Can Struvite Stones in Cats Really Dissolve?

Yes. Suspected sterile struvite bladder stones can often be dissolved completely with an appropriate veterinary diet. The cat must eat the diet exclusively and undergo repeat imaging.

How Long Does It Take To Dissolve Struvite Stones?

Most dissolve in approximately 14 to 21 days. Some dissolve within one week, while selected cases may take up to 56 days.

Are Struvite Crystals Dangerous?

Crystals alone do not always cause disease. They become more concerning when accompanied by urinary pain, blood, stones or urethral obstruction. A male cat repeatedly straining requires immediate care regardless of whether crystals have been identified.

Does My Cat Need Antibiotics?

Only when a clinically significant bacterial infection is confirmed or strongly suspected. Antibiotics do not treat sterile struvite stones.

Can Male Cats Have Their Stones Dissolved?

Yes, provided the cat is not currently obstructed and can be monitored closely. Current consensus considers the risk of obstruction during properly conducted dissolution to be very low, even in male cats.

Final Thoughts

Struvite bladder stones are painful, but they are also among the most treatable feline urinary stones.

The most important points are:

1. Struvite stones are made from magnesium ammonium phosphate.

2. Crystals do not automatically mean a stone is present.

3. Imaging is needed to confirm bladder stones.

4. Stone composition must be predicted before treatment begins.

5. Definitive mineral identification requires laboratory stone analysis.

6. Many feline struvite stones form without bacterial infection.

7. Infection-induced struvite still occurs and requires urine culture.

8. Medical dissolution should usually be attempted before surgery when struvite is likely.

9. The therapeutic diet must be fed exclusively.

10. Both canned and dry therapeutic diets may be effective.

11. Most stones dissolve within approximately two to three weeks.

12. Selected cases may require up to eight weeks.

13. Repeat radiographs should usually be performed every two to three weeks.

14. Stones that do not shrink require reassessment of compliance, infection and mineral type.

15. Calcium oxalate stones cannot be dissolved.

16. Minimally invasive removal should be considered before open surgery where available.

17. Urinary acidifiers should not be added without veterinary direction.

18. Long-term prevention requires appropriate nutrition, hydration and monitoring.

19. A male cat producing only drops or no urine requires emergency treatment.

The mistake that causes the greatest harm is assuming the stone is struvite and starting treatment without confirming that the cat is stable, the urethra is open and the mineral prediction makes sense.

When those pieces are in place, dietary dissolution can spare many cats an operation and produce an excellent outcome.

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ASK A VET™ can help you organise urinalysis results, radiograph dates, dietary compliance and changes in your cat’s urine output while you continue working directly with your veterinary team. A cat that is repeatedly straining, producing only drops or passing no normal urine still requires immediate hands-on emergency care.