Causes of Bladder Stones
Canine urine contains a number of different minerals, or salts, that normally remain dissolved in fluid. When the urine becomes too concentrated, or “supersaturated,” these dissolved salts can precipitate out of the fluid to form solids in the form of crystals. These crystals can damage the lining of the urinary tract, causing blood in the urine (hematuria), and can predispose affected dogs to developing bacterial urinary tract infections. Over time, the mineral crystals can aggregate with organic material (which can include bacteria) and coalesce to form calculi, or what commonly are called stones. When calculi form in any part of the urinary tract, they are referred to as uroliths. For the purpose of our articles, we are going to refer to calculi, and uroliths, as 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, which has a low pH. Urine pH can be affected by a number of things, including diet, hydration, the presence of bacteria/urinary tract infections, certain medications, conformation of urinary tract structures and genetics. Common types of urinary tract crystals and stones are struvite (magnesium ammonium phosphate), calcium oxalate, urate, calcium phosphate, silicate and cystine. The crystals can accumulate to form one stone, many stones, small stones or very large stones, and the surface of these stones can range from smooth to jagged.
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. Annual veterinary check-ups, including routine blood work and urinalyses, can help veterinarians detect abnormal levels of crystals in the urine well before they become symptomatic or form stones. Once detected and removed, stones are best prevented (or at least managed) by dietary changes, including a protein-restricted diet. There are a number of good, commercially available diets to address problems with stone formation and other urinary tract problems. It is also important to keep dogs well-hydrated, because dehydration increases the concentration of canine urine and predisposes the dog to developing crystals and urinary stones.
Urinary tract infections predispose dogs to development of stones in their urinary tracts. The reverse is true as well, underscoring the importance of annual veterinary examinations accompanied by urinalyses and routine blood screening for our companion animals.