Crystals in urine and actual urinary stone disease are different findings. A male cat's anatomy increases the risk of blockage, but not all urinary symptoms in males are caused by struvite stones. Female cats can also develop stones.
When to see a vet urgently
Being unable to pass urine is an emergency. Seek help immediately if:
- Your cat repeatedly strains but passes no urine or only drops.
- The abdomen seems painful and your cat cries, hides or constantly licks their genitals.
- Difficulty urinating is accompanied by vomiting, weakness or not eating.
- Your cat is cold, unusually limp or collapses.
Do not wait for your cat to deteriorate or try to squeeze the bladder empty. You can find a vet near you.
Overview
Struvite forms when urine composition changes, most often in association with alkaline urine and a high mineral concentration. In cats, it can occur as microlithiasis, with grit and crystals, or urolithiasis, with stones. The greatest danger is stones or crystals blocking a male cat's urethra, causing acute urinary retention: a life-threatening emergency.
Urine acidity, concentration and the combined effects of minerals determine how readily struvite precipitates. A crystal is small, whereas a stone is a larger, solid formation. Crystals can also be found in a cat without symptoms or stones. Conversely, a stone may be present even if no crystals are seen in the sample examined.
A urethral plug can contain mucus, inflammatory cells and other protein-rich material as well as crystals. The obstruction is therefore not always caused by a single stone. Idiopathic cystitis, or bladder symptoms without a clear local cause, can also cause similar pain and predispose a cat to blockage.
Causes
- Too much magnesium and phosphorus in the diet.
- An unbalanced diet, including foods high in mineral salts.
- Low water intake and concentrated urine.
- Urinary tract infection, an uncommon cause in cats: unlike in dogs, feline struvite stones are almost always sterile.
- Obesity and lack of exercise.
- Hereditary predisposition.
The effect of feeding cannot be judged from one ingredient or simply from whether food is dry. Minerals are essential nutrients for cats, and a therapeutic diet aims to alter the overall urine composition in a controlled way. Restricting magnesium or phosphorus and acidifying urine yourself do not replace a balanced diet chosen by your vet.
Feline struvite is usually sterile, but infection-related stones also occur. If a bacterial infection is suspected, it is confirmed with an appropriate urine sample and culture. Symptoms of inflammation or a crystal alone do not indicate a need for antibiotics. Diet and other predisposing factors are assessed for the individual cat.
Risk factors
- Male cats, particularly those that are neutered and overweight; the male urethra is narrower than the female urethra, but neutering itself does not narrow it.
- Middle-aged and older cats.
- Cats eating only poor-quality dry food.
- Cats with chronic bladder inflammation or urinary tract infections.
The risk of blockage and the risk of forming a struvite stone are not the same. Struvite stones are often diagnosed in young adult and middle-aged cats, so old age alone is not a characteristic risk factor for this stone type. The general claims about heredity and food quality in the list cannot establish the cause of an individual cat's stones. Previous stone analysis provides more information than sex alone.
Typical symptoms
- A frequent, painful urge to urinate.
- Passing small amounts of urine or none at all.
- Blood in the urine (haematuria).
- Licking the genitals.
- Restlessness and distressed meowing.
- A tense, tender abdomen.
- With obstruction, apathy, vomiting, refusal to eat and a life-threatening condition within 24–48 hours.
The stated 24–48 hours is not a safe waiting period. A complete blockage can disrupt kidney function and blood electrolyte balance before you notice that your cat is very ill. Painful, unsuccessful straining is enough reason to contact a vet immediately.
Straining in the litter tray can be mistaken for constipation. Check whether your cat is actually producing urine clumps, but do not delay leaving to collect a sample or be certain of what you have seen. In a multi-cat home, urine visible in the tray may also belong to another cat.
Complications and consequences
- Acute urinary retention from urethral obstruction.
- Dilation of the renal pelvis and kidney failure.
- Chronic bladder inflammation.
- Repeated recurrence of stones.
- Death if help is not obtained in time.
During a blockage, potassium can build up in the blood and disturb the heart rhythm. Bladder damage is also possible. Emergency assessment therefore considers the whole cat, rather than urine flow alone. Fluid treatment and relief of the blockage require monitoring of circulation and electrolytes according to the situation.
Diagnosis at the vet
- Urinalysis, including pH, crystals and bacteria.
- Blood tests, including kidney values and electrolytes.
- Ultrasound of the bladder and kidneys for stones, grit and inflammation.
- X-rays: struvite stones are radiopaque and show up well.
- Urine bacterial culture.
Interpreting the sample
Urine testing includes specific gravity, a measure of concentration, as well as pH, cells and crystals. The age and storage of the sample affect results: crystals can form in the container after delayed examination or cooling. Report the collection time and ask for storage instructions beforehand if collecting a sample at home.
Crystal numbers and pH alone do not confirm a stone's composition. Crystals in a cat without symptoms are also assessed in context, rather than automatically treated as disease. However, substantial or repeated findings and accompanying symptoms can affect the need for dietary changes and further investigation.
Where possible for the cat's condition, a culture sample is preferably collected aseptically directly from the bladder. This reduces contamination by external bacteria. The aim is to obtain it before antibiotics are given. Even a positive result is interpreted alongside symptoms and other findings.
Imaging and stone analysis
Ultrasound and X-rays complement each other. They assess the location, size and number of stones and other urinary tract changes. A dense stone visible on an X-ray may be consistent with struvite, but calcium oxalate is also visible. Visibility alone therefore cannot reliably identify the correct dissolution treatment.
If a stone is recovered, its mineral composition should be analysed. Composition affects treatment and prevention of recurrence. Blood tests particularly assess kidney function and changes caused by obstruction. Recurrent symptoms are investigated again, because a new episode may not have exactly the same cause.
Treatment
A vet usually relieves the obstruction with a catheter under sedation or general anaesthesia. Pain is treated and dangerous fluid and electrolyte disturbances are corrected at the same time. Your cat may need hospital care and monitoring until they can urinate independently. If urine cannot pass, treatment does not wait for a diet to take effect.
Dissolving struvite stones
In a suitable, stable case, struvite stones can often be dissolved with a therapeutic diet chosen for this purpose. This distinguishes them from calcium oxalate stones, which cannot be dissolved in the same way. Dissolution is not suitable for every stone or patient. Your vet also assesses whether another removal method is needed.
The therapeutic food must make up the entire planned diet. Other foods, treats and supplements can alter its effect. Report other diseases and any diets prescribed for them before switching. Make sure your cat actually eats the agreed food; report a failure to eat, rather than leaving your cat to wait until they eventually accept it.
Progress is monitored through imaging and urine tests. Shrinking stones support the effectiveness of treatment. If they do not change, the assumed composition, adherence to the diet and possibility of infection are reassessed. Symptom improvement or disappearance of crystals from a sample alone does not confirm that the stones have dissolved.
Ongoing care and prognosis
Infection-related struvite also requires treatment targeted at the bacteria. Antibiotics are not given as a precaution for sterile struvite. Removing a stone surgically or by another method also does not mean that the tendency that caused it to form has gone.
After discharge, monitor urine volume, straining, appetite and alertness. If urination becomes blocked again, this is a new emergency. The ongoing diet and follow-up checks are agreed according to stone type and your cat's other needs. Good monitoring can detect recurrence before a severe blockage, but complete protection cannot be promised.
Prevention
- Feed your cat a specialist diet intended to prevent urinary stones.
- Keep fresh water available; drinking fountains increase water intake.
- Manage weight and provide exercise.
- Arrange regular urine tests for an at-risk cat.
- Prevent chronic bladder inflammation.
A specialist diet is chosen for the diagnosed problem; not every healthy cat or incidental crystal finding is treated with the same diet. Do not add urine-acidifying supplements yourself. A dissolution diet and a long-term prevention diet may serve different purposes, so ongoing feeding is agreed according to test results.
Wet food and an appropriate amount of water added to food can increase fluid intake. Also offer clean water bowls in quiet places. Some cats prefer a fountain, but this does not guarantee increased drinking for every cat. Observe your own cat's preferences and the suitability of the diet.
Keep litter trays clean and easily accessible. Enough space, suitable litter and the ability to use the tray without interference from another cat support normal urination. A calm environment also helps manage idiopathic cystitis, but does not dissolve existing stones on its own.
Important for cat owners
Struvite stone disease is a common and dangerous problem, particularly in neutered male cats. Remember that any difficulty urinating in a male cat is an emergency. Urgent veterinary help saves lives and prevents serious complications. Long-term prevention includes diet, weight management and regular veterinary monitoring.
This article provides general information and does not replace veterinary care. If your cat cannot pass urine, contact a vet or emergency service immediately.
Frequently asked questions
Do struvite crystals always mean urinary stones?
No. Crystals can also be found in healthy cats and can form in a stored sample. Stones are confirmed by imaging, and the result is assessed alongside symptoms.
Can struvite stones be dissolved with diet?
Often, if the presumed stone composition and your cat's condition are suitable for dissolution. Imaging monitors treatment; a blockage is not treated by waiting for food to work.
Does struvite require an antibiotic?
Usually not, because most feline struvite stones are sterile. An antibiotic is chosen if there is a bacterial infection that requires treatment.
Can I wait until morning if no urine is coming out?
No. Unsuccessful straining to urinate may mean a life-threatening blockage. Contact an emergency vet immediately.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- 2025 iCatCare consensus guidelines on the diagnosis and management of lower urinary tract diseases in cats, Journal of Feline Medicine and Surgery, accessed 2026-11-03.
- Urolithiasis in Cats, Merck Veterinary Manual, accessed 2026-11-03.
- Dissolving feline struvite stones, University of Minnesota College of Veterinary Medicine, accessed 2026-11-03.
- Urinary Obstruction in Male Cats, American College of Veterinary Surgeons, accessed 2026-11-03.
- Blocked bladder in cats, PDSA, accessed 2026-11-03.
- Urinalysis, Merck Veterinary Manual, accessed 2026-11-03.
- Hydration, Cornell Feline Health Centre, accessed 2026-11-03.
- Litter Boxes, The Ohio State University Indoor Pet Initiative, accessed 2026-11-03.
- ISCAID guidelines for the diagnosis and management of bacterial urinary tract infections in dogs and cats, The Veterinary Journal, accessed 2026-11-03.
- Feline Lower Urinary Tract Disease, Cornell Feline Health Centre, accessed 2026-11-03.