Introduction
Bladder stones, medically referred to as uroliths or calculi, are accumulations of minerals and other substances in the urinary bladder. Uroliths can occur in any part of the urinary tract, from the kidneys to the ureters to the urinary bladder and ultimately to the urethra. They become problematic when they obstruct the ureters or urethra, blocking the normal outflow of urine – a condition that can become life-threatening if not treated immediately.
How Bladder Stones Affect Dogs
Uroliths are more common in older animals and in males, although they have been reported in dogs of both genders and all ages. Many affected dogs 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 quickly develop and rapidly worsen. The dog will urinate (or try to urinate) frantically and frequently and will strain to do so, although little or no urine will be excreted. They typically exhibit signs of pain, such as repeatedly turning and looking at their abdomen and hindquarters, running to and from their normal “pottying” place, pacing and eliminating in inappropriate areas.
Causes of Bladder Stones in Dogs
Bladder stones usually are composed of concentric layers of microscopic mineral crystals that are deposited sequentially from the center of the stone outward. 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 that has a high pH (alkaline urine), while others form in acidic urine. Urine pH of is 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, among others. Common types of urinary calculi 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.
Prevention of Bladder Stones
Any obstruction of the canine 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 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.
Special Notes
Urinary tract infections predispose affected animals to development of urinary tract stones. The reverse is true as well, underscoring the importance of annual veterinary examinations accompanied by urinalyses and routine blood screening for our companion animals.