Urinary Crystals in Dogs

Sometimes crystals can form in a dog's urine. These are deposits of various minerals, and their formation is influenced by the characteristics of the urine, which in turn are affected by diet, among other factors.

The main problem with these crystals is that they can grow large enough that the dog can't pass them on its own, which can then cause problems in the urinary system, even as serious as a complete obstruction.

What Are Urinary Crystals?

There are different causes behind the formation of these crystals. One very common one is cystitis. Cystitis is a bacterial infection of the bladder. Bacterial colonies are structures where minerals in the urine can more easily deposit, forming crystals.

On the other hand, some metabolic diseases lead to a higher concentration of minerals in the urine, with the resulting risk of crystal formation. The same happens with diet. Dogs on diets higher in minerals have a greater chance of developing urinary crystals.

Breeds Predisposed to Them

Crystals can potentially form in any dog. But some breeds show a higher genetic predisposition. These are the Dalmatian, Bichon Frisé, Cocker Spaniel, Lhasa Apso, Yorkshire Terrier, Shih Tzu, German Shepherd, Dachshund, Golden Retriever, and Labrador, among others.

Symptoms of Urinary Crystals

One symptom pointing to the presence of urinary crystals is hematuria, meaning blood in the urine. There are other conditions with hematuria as a symptom too, so if we notice blood in our dog's urine, or a reddish color, we need to see the vet. In the case of crystals, the bleeding is due to the damage they cause in the urinary tract.

It's not unusual for crystals to clump together, forming what's known as stones, or more commonly, "piedras." Depending on their location and size, they can completely block the urinary system. In that case, the main symptom will be the dog not urinating, or doing so with difficulty, passing small amounts more often than usual.

In addition, abdominal pain is common, and the dog may adopt a straining posture without managing to urinate. Obstructions are more common in males and can end up damaging the kidneys, causing vomiting, loss of appetite, and listlessness. Of course, even suspecting a partial obstruction is enough reason to see the vet.

How to Identify Urinary Crystals

If you think your dog may have urinary crystals, see the vet. This professional can confirm the diagnosis. A urine sample is needed for this. We can bring it from home, ideally collected in a sterile container sold at pharmacies, or the vet can extract it, sometimes directly from the bladder.

The urine's pH can be measured, and the presence of blood or infection detected, along with visualizing the crystals themselves. Depending on which mineral forms them, they'll have a different appearance. Crystals can be seen under a microscope. Stones are visible with the naked eye.

Urinary pH and Urinary Crystals

pH, or hydrogen ion potential, is an index, from 0 to 14, that indicates whether an environment is acidic, alkaline, or neutral. In an acidic environment, it's below 7; in a basic or alkaline one, above 7; and in a neutral one, it equals 7. This matters when crystals are present, since the pH type allows certain minerals to precipitate over others.

As a result, it also matters for treatment, since it can be modified. For example, if a crystal forms in alkaline urine, giving a food that acidifies the pH can dissolve the crystals and prevent them from forming again. Besides pH, the urine's temperature and density also influence crystal formation.

Types of Urinary Crystals

Several minerals can precipitate in the urine and form crystals. So, in dogs we mostly find struvite crystals, but also calcium oxalate, ammonium urate, cystine, or, less commonly, silica or calcium phosphate crystals. These are the characteristics of the most common ones:

• Struvite crystals: made up of phosphate, ammonia, and magnesium, with a very recognizable coffin shape. They appear in alkaline urine.
• Calcium oxalate crystals: also fairly common, with the downside that they don't dissolve. They form in acidic urine.
• Ammonium urate crystals: derived from uric acid, they can be found in both acidic and neutral urine. They're the typical crystal seen in the Dalmatian.
• Cystine crystals: very uncommon, hexagonal in shape, and appear in acidic or neutral urine.

What Is the Treatment for Urinary Crystals?

Treatment will depend on the type of crystal identified. Struvite crystals, the most common, can be dissolved through medication, a specific diet formulated for this problem, and increased water intake. Ammonium urate or cystine crystals also dissolve.

In addition, it's recommended to take the dog out more often. Increasing how often it urinates prevents the urine from sitting too long in the bladder, another factor that favors crystallization. With these measures, following the diet for a few weeks, is usually enough to control the problem.

But sometimes, stones form that need to be surgically removed. In addition, crystals like calcium oxalate don't dissolve. So, if the dog can't pass them, they also need to be removed. Of course, if there's infection or any other symptom, that will also need to be treated by the vet.

Bibliography Baciero, Gemma. "Urolitiasis canina". Axón veterinaria nº 29. pp. 20-25. Carlson and Giffin. 2002. Manual práctico de veterinaria canina. Madrid. Editorial el Drac.