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Struvite Bladder Stones in Cats

Understanding Your Pet's Medical Diagnosis

What is struvite urolithiasis in cats?

Struvite urolithiasis in cats is the presence of stones (uroliths) in the urinary tract. Struvite plugs may develop in the urethra (the tube that carries urine from the bladder). The stones or plugs are composed of mineral salts that gather around organic material. Struvite is a chemical composed mainly of magnesium. Struvite is differentiated from other types of stones such as calcium stones.

Struvite stones in the kidneys or ureters (the tubes from the kidney to the bladder) are more common in females. Struvite urethral plugs (in the tube that carries urine from the bladder) affect males almost exclusively. The normal small diameter of the urethra in male cats makes blockage of urine flow (obstruction) by the plugs a life-threatening problem. If a cat is unable to urinate, emergency veterinary care is required.

What causes struvite urolithiasis?

Urinary stones can be infected or sterile. The cause of infected stones usually is a urinary tract infection. Generally struvite stones are sterile. Suggested causes of sterile stones include:

Mineral composition of the diet
Moisture content of the diet
Quantity of food
Feeding schedule or lack of scheduled feedings
Concentrated urine
Retention of urine in the bladder
The prevalence of struvite urolithiasis has been declining since the mid1980s because special diets were designed to dissolve and prevent this type of stone.

What are the signs of struvite urolithiasis?

Some cats do not exhibit signs while other cats may exhibit one or more signs. The signs depend on the location, size, and number of stones or plugs. Typical signs include change in frequency of urination (ranges from increased frequency to lack of urination), urinating in unusual places, difficulty urinating, blood in the urine, and sometimes passing small stones. Cats with stones that block urine flow will have additional signs such as poor appetite, vomiting, or pain. Kidney failure can be a complication of urinary tract stones.

How is struvite urolithiasis diagnosed?

On physical examination, the veterinarian will palpate (feel) the bladder, checking to see if it is thickened, firm, contracted, or enlarged. Some stones or plugs in the urethra may be detected by palpating the penis, but most stones cannot be felt on physical examination. Radiographs (X-rays) or ultrasound can identify the location, size, and number of stones. Other tests such as urinalysis, urine culture, and analysis of any stones or plugs may be needed. Blood tests will help in diagnosing any accompanying kidney disease.

How is struvite urolithiasis treated?

Treatment of struvite urolithiasis depends on the location of the stones or plugs and the severity of the problem. Sometimes struvite stones or plugs can be dissolved with special diets and/or medications on an outpatient basis. If analysis of the stones or plugs determines that the stones are struvite, a magnesium-restricted diet may be prescribed. If infected stones are identified, the pet is treated with antibiotics.

Often stones cannot be dissolved, especially those in the kidneys or ureters; and more aggressive treatment is needed, necessitating hospitalization. Your veterinarian may be able to induce the stones to pass by flushing the bladder with sterile fluids. If stones cannot be dissolved, if they fail to pass, or if they recur, surgery may be needed. If the stones or plugs cause blockage of urine, the blockage must be relieved. Passing a catheter and providing a means for urine flow can provide immediate relief. Occasionally surgery may be needed to relieve the blockage. Additionally, some cats will need fluid therapy. The veterinarian will recommend the necessary treatment for each case. Recurrent struvite urolithiasis may be prevented by the use of magnesium-restricted diets.

What is the prognosis for cats with struvite urolithiasis?

The prognosis (outcome) depends on the location and severity of the stones and on the choice of treatment. Stones treated with diet or medications will take four-to-ten weeks to dissolve. Unfortunately, not all stones will dissolve with medical treatment. Cats with infected stones need to be treated with antibiotics until the urinary tract infection is cured. Cats need to be re-evaluated periodically for a repeat urinalysis, urine culture, or X-rays, if needed. The prognosis for the more severely affected cats is variable. If the cat is in kidney failure, aggressive treatment will be required. If the urinary tract is blocked, the problem is life threatening and emergency veterinary care is required. The outcome in these cases will depend upon the degree of damage to the urinary tract and the promptness with which veterinary care is sought.

The information on this page was obtained from the site www.vetmedcenter.com