Minerals naturally present in your cat’s urine can sometimes clump together, forming tiny crystals. When these crystals aggregate, they develop into uroliths, commonly known as urinary stones or bladder stones. These stones can occur anywhere within the urinary system, including the kidneys, ureters, bladder, or urethra. It’s been observed that certain types of Bladder Stones In Cats have become more prevalent in recent years, and while the exact cause remains under investigation, dietary factors are being closely examined as a potential link.
Veterinary researchers are still working to fully understand the underlying causes of bladder stone formation in cats (further details below in “Why Cats Develop Bladder Stones“). There are various types of bladder stones, each with a unique composition of minerals. Struvite, calcium oxalate, and urate stones are among the most frequently encountered. The development of these and other types of stones is often condition-dependent, potentially triggered by mineral imbalances or disruptions in the urine’s chemical balance, which normally prevents stone formation. The urinary tract environment itself can also play a significant role. Factors such as urinary tract infections, diet, digestion, urine volume, urination frequency, medications, and genetics can all influence these conditions.
Why Cats Develop Bladder Stones
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Cats naturally produce highly concentrated, acidic urine, which predisposes them to urinary tract stone formation. This risk is heightened when certain minerals are either in excess or deficient. Diet, inflammation, infection, and the urine’s pH level can all contribute. A bladder stone typically has a hardened core with layers accumulating around it. The initial trigger for stone formation isn’t fully understood, but it’s likely that an overabundance of stone-forming minerals in the urine leads to the creation of small crystals that then bind together. Once formed, the stone gradually increases in size over weeks or months.
Cats can also develop smaller stones resembling sand or toothpaste consistency. These small stones, crystals, and other urinary components can form “plugs” that obstruct the urinary tract, especially the urethra. Veterinarians identify stones based on their mineral composition. In cats, struvite (magnesium ammonium phosphate) and calcium oxalate stones are the most common. Calcium oxalate stones are now the most frequently found type in the urinary tract and kidneys, although their precise cause is still unknown. Interestingly, some diets designed to manage struvite stones might inadvertently contribute to the formation of calcium oxalate stones.
Cats with very small bladder stones may not exhibit any noticeable symptoms. However, larger stones in the lower urinary tract can disrupt urination or irritate the urethra lining. This can lead to symptoms such as straining to urinate, blood in the urine (hematuria), and slow or painful urination (dysuria). Kidney stones, while less common in cats, usually remain asymptomatic unless they cause kidney inflammation or migrate into the ureter.
If a stone obstructs a ureter, it can cause vomiting, lethargy, or abdominal pain, particularly in the kidney area. Severe pain is more likely when both ureters are suddenly and completely blocked, leading to fluid buildup and kidney enlargement. Pain might be the only sign of a ureteral stone on one side, but it can be challenging to detect in cats. Untreated ureteral obstruction can lead to kidney damage and, eventually, kidney failure.
Veterinarians can sometimes palpate bladder stones during an abdominal examination. Urethral stones may be detected during a rectal exam or catheterization attempt. Multiple stones can be present simultaneously, so if one is found, a thorough examination of the entire urinary tract is crucial. X-rays can detect stones as small as 3 millimeters. Veterinary diagnostic procedures also include urinalysis, urine culture, and potentially ultrasonography or other specialized imaging.
Treatment and prevention strategies for bladder stones depend on the stone type and location. Options include surgery, specialized diets, lithotripsy (using sound waves to break down stones), and medication. Removed stones are often sent to a laboratory for mineral analysis. This analysis helps determine the stone type, guiding the veterinarian in prescribing appropriate medications and dietary changes to prevent recurrence. Cats undergoing treatment for uroliths require close monitoring and regular follow-up testing. Managing urinary tract infections, avoiding unnecessary mineral and vitamin supplements, and ensuring adequate water intake are also vital aspects of prevention.
Urethral Obstruction: A Critical Emergency
Bladder stones can become lodged in the urethra, blocking urine flow from the bladder. This condition, known as urethral obstruction, is more common in male cats and constitutes a medical emergency. It can develop suddenly or gradually over days or weeks. Initially, a cat might frequently attempt to urinate but only produce a thin stream, a few drops, or nothing at all. They may exhibit extreme pain and vocalize when trying to urinate.
Complete urethral obstruction leads to a buildup of toxins in the body within 24-48 hours, resulting in depression, appetite loss, vomiting, diarrhea, dehydration, arrhythmias (irregular heartbeats), coma, and potentially death within approximately 72 hours. Urethral obstruction requires immediate veterinary intervention.
Treatment focuses on relieving the obstruction, either by gently pushing the stone back into the bladder using a catheter or by surgically removing it. If the stone is pushed back into the bladder, surgical removal is usually recommended to prevent it from re-entering the urethra.
For Further Reading
For more in-depth information, consult professional resources on urinary stones in animals.
