Bladder stones, medically referred to as uroliths or bladder calculi, are accumulations of minerals and other substances in the urinary bladder. Uroliths can occur in any part of a cat's urinary tract, from the kidneys to the urethra, although the urinary bladder is the most common site of stone formation.
How Bladder Stones Affect Cats
Bladder stones can predispose affected cats to recurrent and painful urinary tract infections. They also can cause urethral obstruction, which is a medical emergency and a potentially life-threatening condition if left untreated. Uroliths are more common in older male cats, although they have been reported in cats of both genders and all ages. Some affected cats show no outward signs of discomfort. Bladder stones are often first detected during routine urinalyses examinations, when crystals of the calculi and blood from physical disruption of the bladder lining are detected microscopically. When the stones cause a partial or complete blockage, clinical signs develop quickly and rapidly worsen. The clinical signs are typically the same regardless of the particular composition of the stones. Affected cats will urinate (or try to urinate) frantically and frequently and will strain to do so, although little or no urine will be excreted.
Causes of Bladder Stones in Cats
Bladder stones develop when the urine of susceptible cats is oversaturated with microscopic mineral crystals. Over time, these crystals aggregate with organic material (which can include bacteria) and coalesce to form calculi, or stones. The pH of urine contributes to stone formation; some crystals form in urine with a high pH (alkaline urine), while others form in acidic urine. Urine pH can be affected by a number of things, including diet, hydration, the presence of bacteria/urinary tract infections, certain medications, structural conformation of urinary tract components and genetics. Common types of urinary calculi in cats are struvite, calcium oxalate, urate salts, calcium phosphate, silica and cystine. These can accumulate to form one stone, many stones, small stones or very large stones. Certain breeds are predisposed to developing stones with a predominant mineral type.
Preventing Bladder Stones
Any obstruction of the feline urinary tract is potentially fatal. A well-balanced, high quality diet can promote urinary tract health. Regular veterinary check-ups, including routine blood work and urinalyses, can help veterinarians detect bladder stones well before they become symptomatic. Fortunately, stones are easily diagnosed through radiography (x-rays) and usually can either be dissolved with diet and medical management or removed surgically. Once detected and removed, subsequent stones can be prevented or at least managed by dietary changes.
Urinary tract infections predispose affected animals to development of urinary stones. The reverse is true as well, underscoring the importance of annual veterinary examinations accompanied by urinalyses and routine blood screening for our companion cats.