Why do Struvite Uroliths form?

Several factors are needed to form a struvite stone. Struvite is a urinary mineral composed of ammonium, phosphate and magnesium. These three substances are common in urine, but when they are in high enough concentrations they bind together to form crystals. Ultimately, pets with very concentrated urine of a basic (high) pH can result in the congregation of struvite crystals resulting in a stone. Infections of the bladder that change the urine pH can predispose dogs and cats to struvite bladder stones.

How do you diagnose struvite stones?

Although a urinalysis can provide clues (struvite crystals and high urine pH), and an ultrasound or x ray can confirm the presence of stones, the only way to know the exact stone type is to retrieve the stone(s) surgically (cystotomy) and have a laboratory analyze it.

How do you treat struvite stone?

Struvite stones can be treated in one of two ways: surgically or dissolved through diet.

Surgery – this is the most direct method of removal. The advantage is that the stones are removed and the healing may commence all in one day. This allows the stones to be collected and analyzed to confirm their type.

Dietary Dissolution – There are several therapeutic prescription foods designed to dissolve struvite crystals and stones. They act by creating a bladder environment favorable to dissolution. In order to proceed with this form of treatment, the patient should be female (as the stone dissolves and becomes smaller, we do not want it lodging in the narrow male urinary tract causing obstruction). Monthly urine checks (looking for signs of infection which can cause stone formation) and imaging of the bladder (by x ray or ultrasound) must be performed to know when the stones are gone and to know if this method is helping (dietary dissolution does not work for every pet). Once we know the stones are gone, patients are put on a “maintenance” therapeutic diet to help reduce the risk of reforming these stones. On average it takes 3-4 months for stones to dissolve. If at any time your pet makes attempts to urinate without production of urine, contact your veterinarian immediately – urinary obstruction as stones dissolve is a medical emergency!

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