Abnormal Crystals in Urine

Crystal Types

• Urine can contain many types of crystals, but the ones that cause problems are calcium oxalate and struvite crystals. These are the crystals that have the potential to aggregate and form stones, which cause tremendous discomfort and bloody urine, and must be surgically removed. Calcium oxalate crystals are more common in cats, and form in urine that is too acidic, while struvite crystals are more common in dogs, and form in alkaline urine. Various other crystals can appear transiently as well, for example sulfa crystals are sometimes seen in dogs taking sulfa drugs, but they dissolve once the medication is discontinued. Cholesterol crystals are also occasionally seen, and may be indicative of a metabolic disorder or nothing at all.

Secondary Infections

• Urine crystals tend to harbor bacteria. Each time the dog urinates, the crystals can potentially scrape the walls of the urethra, causing tiny abrasions. These abrasions allow the bacteria a place to take hold and flourish, causing an infection. This is especially serious when struvite crystals are present, since bacterial infections often increase the alkalinity of the urine, exacerbating the problem. To make matters worse, waste metabolized by bacteria contains chemicals that increase the formation of struvite crystals.

Blockages

• While tiny amorphous crystals pass with the urine and large stones stay in the bladder, the danger lies with the medium-sized crystal aggregates or small stones. These are small enough to leave the bladder, but too large to pass through the urethra, so they often become lodged at the urethral opening. This usually happens in males, especially cats, and creates a dire emergency because the animal will be unable to pass urine. If left untreated, the bladder will eventually rupture, spilling a heavy load of toxins into the bloodstream, causing death.

Treatment

• Urine crystals are treated with a multifaceted approach. Bacterial infections are eliminated with antibiotics, and an appropriate food is prescribed that will balance the pH of the urine. Struvite crystals may actually be dissolved in this manner, but calcium oxalate crystals must be flushed from the bladder, while new ones are prevented from forming. Keeping the animal well-hydrated during treatment allows the bladder to flush out both the crystals and dead bacteria more efficiently.

Prevention

• An animal who has had urine crystals once is likely to have them again, so they must often be kept on a specialized diet. Feeding your pet canned food instead of dry increases the amount of moisture he takes in, and is thought to help prevent urine concentration that can contribute to crystal formation. Including a urinalysis as part of your pet's annual physical will enable your vet to catch potential problems before they become serious.