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Calcium Phosphate Urolithiasis in Cats

When stones (uroliths) form in the urinary tract, it is referred to as urolithiasis. There are various types of these stones seen in cats -- among them, those made from calcium phosphate. Also known as apatite uroliths, calcium phosphate stones are more often found the kidneys than the urinary bladder.

Symptoms and Types

The symptoms may vary depending on the location, size, and number of stones within the urinary tract. In fact, some cats display no outwardly visible signs of the issue; it is only discovered later during a routine checkup, if at all. The following are some typical symptoms associated with calcium phosphate urolithiasis:

• Increased urination (polyuria)
• Difficulty urinating (e.g., dribbling of urine)
• Pain when urinating
• Blood in urine

Causes

• Excessive calcium in diet
• Excessive use of mineral supplements (e.g., vitamin D)
• Various kidney diseases/infections

Diagnosis

After completing a complete medical history of your animal, your veterinarian will perform a physical exam on the cat, including a blood chemical profile, a complete blood count, a urinalysis, and an electrolyte panel. Although the results of these tests may be normal, there are exceptions. In some cats, the biochemistry profile may show abnormally high levels of calcium in the blood. In cats with severe kidney damage or urinary tract blockage, high levels of waste products like urea may be found in the blood.

Biochemical changes related to underlying disease are also helpful in diagnosing the underlying disease or condition. Additionally, microscopic urine examination is useful in identifying the type of stone.