Overview

Struvite bladder stones are one of the most common types of stones in dogs, especially in females. Also known as uroliths, struvite stones are rock-like formations of minerals. They most commonly form in a dog’s bladder or urethra from urinary tract infections (UTIs) and alterations in the urine pH.

The clinical signs of struvite stones are similar to signs of a UTI, including frequent or bloody urination. Treatment commonly involves antibiotics and veterinary therapeutic diets to dissolve the stones, but sometimes may require surgical removal. Struvite stone recurrence can be decreased by preventing UTIs and dietary changes.

Cause

In dogs, struvite stones are typically caused by UTIs and urease-producing bacteria. Struvite crystals form when the pH of urine becomes more alkaline and concentrated. When these changes occur, certain substances become supersaturated and promote the growth of struvite crystals. As more crystals form, they stick together and form an organized stone or multiple stones. Bacteria can get trapped in between layers of the stone as it enlarges.

Struvite stones are more common in young, female, small-breed dogs, though any size or breed of dog may be affected.

Clinical Signs

Some dogs may not show any signs, but the most common clinical signs may include:

• Bloody urine
• Increased frequency of urination
• Straining to urinate
• Urinary accidents in home

In some cases, a struvite stone could cause a urinary obstruction by blocking urine from leaving the bladder or urethra. Much more severe signs could occur if there is a urinary obstruction, including vomiting, abdominal pain, lethargy, dehydration and the potential for bladder rupture. A urinary obstruction can be potentially life-threatening and is considered a medical emergency.

Diagnosis

Your veterinarian may be able to feel bladder stones during their physical exam and palpation of your dog’s abdomen if the stones are large enough. They may recommend performing the following tests to diagnose struvite stones:

• Urinalysis
• Urine culture and sensitivity
• Abdominal X-rays or ultrasound
• Urolith analysis

Treatment

Struvite stones are treated medically with antibiotics and a therapeutic diet to dissolve the stones, such as Hill’s c/d, Royal Canin Urinary SO, and Purina Pro Plan UR. These diets have a reduction in magnesium, phosphorus and protein. They also help to acidify and dilute the urine. Dissolving struvite stones can be effective in 8-12 weeks or sooner.

Your veterinarian may recheck urine samples intermittently while dissolving the stones and x-rays every four weeks to ensure the stones are appropriately decreasing in size and number. In some cases, there may be more than one composition of stone, which may affect the treatment plan and dissolution process. If the stones are not dissolving entirely or there is a risk of urinary tract obstruction, bladder surgery to remove the stones (cystotomy) may be necessary. In other cases, a nonsurgical procedure can be performed by a specialist called lithotripsy, which aims to break down the stones into tiny fragments.

Outcome

The prognosis for struvite stones is generally good with an appropriate and diligent treatment plan. Dietary therapy with a dissolution diet alone may fail if UTIs are not appropriately treated or if the urinary stones are a mixed composition of stones other than struvites. Most dogs will require lifelong management to prevent the recurrence of stones.

Prevention

Struvite stone prevention focuses on preventing recurrent UTIs by frequently monitoring urine samples, making dietary changes, encouraging water consumption with canned food and adding water to dry food. Therapeutic diets used to prevent struvite stones aim to make the urine more acidic, increase diuresis (thirst and urination) and are generally lower in protein, phosphorus and magnesium.