What Are Bladder Stones and Crystals in Cat Urine?
Bladder stones and crystals are solid waste particles that form in the urine. Bladder stones and crystals form when the concentration of waste product in the urine is high enough to cause those waste products to become solid particles. The smallest particles first appear as crystals that can only be seen under a microscope, but over time those crystals can get bigger, and eventually can become stones as big as the bladder itself.
Stones or crystals can be found in the kidneys in the tube that connects the kidney to the bladder (ureter), in the bladder itself, or in the tube that connects the bladder to the outside of the body (urethra). Stones that block or slow the flow of urine out of the kidneys can lead to signs of kidney disease, and a complete urinary blockage is an urgent, life-threatening condition.
What Is the Difference Between Crystals and Bladder Stones?
Crystals are the building blocks of bladder stones. There are different types of crystals and stones that can form depending on various factors, such as the acidity of the urine, the concentration of the urine, genetic factors, diet, and other conditions. It is also possible to have a stone that is made up of more than one type.
The following are some of the crystals/stones that can occur in cats:
- Struvite: Also called magnesium ammonium phosphate stones, struvite is one of the two most common stones in cats. This is due to a multitude of factors such as breed, sex, and diet.
- Calcium oxalate: This forms from the combination of calcium waste and oxalate waste in the urine, and are most common in middle-aged, older, neutered, male cats, or in Persian or Himalayan breeds.
- Urate: This is the waste product from the breakdown of purine, a compound found in certain foods such as fish, red meat, and turkey.
- Xanthine: This is considered rare and forms from a waste product usually associated with allopurinol use (a medication used to treat other conditions).
- Cystine: A condition that is also rare, Cystine is caused by a hereditary condition called cystinuria that leads to the formation of these crystals/stones.
- Silica: This is very uncommon and possibly related to dietary intake of certain grains.
Symptoms of Bladder Stones and Crystals in Cat Urine
- Increased frequency of urination
- Straining to urinate
- Urinating small amounts of urine at a time
- Blood in the urine
- Urinating outside the litterbox
- Signs of a urinary blockage include the inability to urinate, or to urinate very small amounts of urine. Additional symptoms are lethargy, vomiting, and lack of appetite.
- Signs of pain that include crying, lethargy, tense body posture, hiding, and abnormal facial expressions.
Causes of Bladder Stones and Crystals in Cat Urine
The exact cause of crystals/stones is unknown, but there are several factors that are associated with the formation of bladder crystals and stones. The importance of each factor may change depending on the type of crystal/stone. The most common factors are sex, breed, age, diet, and underlying health conditions.
For example, liver dysfunction is a possible predisposing factor of urate crystals/stones. Struvite stone formation is less specific, and is associated with multiple factors, including breed, sex, and low protein diets. Calcium oxalate stone formation is associated with factors such as age, sex, breed, and dietary intake/absorption of calcium.
How Veterinarians Diagnose Bladder Stones and Crystals in Cat Urine
Diagnosis of a stone, crystals, or a blockage includes the following diagnostic tests:
- Bloodwork to look for underlying conditions that may cause certain crystals or stones, or to evaluate the presence/severity of a blockage
- Urinalysis to evaluate the urine environment including the concentration of the urine, the acidity or non-acidity of the urine, and the presence of infection or crystals
- Imaging such as X-rays or ultrasound to visually look for stones
Treatment of Bladder Stones and Crystals in Cat Urine
Treatment of crystals/stones depends on the type of crystal/stone, the size and location of the stone, and the cat’s history. Female cats are often able to pass small stones, either on their own or with a flushing procedure called voiding urohydropropulsion. Male cats, however, are at higher risk for a urinary blockage, even with very small stones. Some stones are dissolvable within two-to-four weeks of starting a prescription diet, however larger stones can dissolve to a small enough size that they can also become a risk for urinary blockage. Stones must be removed surgically if they are too big and not able to dissolve.
If a stone is blocking the flow of urine (most common in male cats), a catheter is passed to flush the stone back to the bladder, and then the stone must either be dissolved or surgically removed to prevent another blockage. A blockage event is life threatening and typically requires several days of hospitalization to stabilize your cat, and one-to-two weeks for a full recovery.
Recovery and Management of Bladder Stones and Crystals in Urine
The recovery of a cat from bladder stones or crystals depends on the type of stone and the cat’s health history. Diet is the most common management strategy since there are several commercial diets designed to treat and/or prevent the most common types of crystals/stones including:
Increasing water intake is another strategy, as crystal/stone formation is more likely in concentrated urine. Feeding canned food is an efficient way to also increase water intake.
Some stones may be treatable with medications, but many of them need further research in cats. For example, potassium citrate and thiazide diuretics have been considered possible options for preventing calcium oxalate stones, but more studies are needed to evaluate their efficacy.
Frequently, a strict diet change and increasing water intake can prevent recurrence, but in some cases, crystals/stones will still recur. In males that develop frequent urinary blockages, a surgical procedure called a perineal urethrostomy may be done to widen the urethra. Keep in mind, annual exams, including routine urinalysis, can help establish what is normal for your pet and if your pet may be predisposed to urinary stones.
Featured Image: iStock.com/urbancow
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