Uroliths

Bladder Stones

Struvite:  The most common uroliths in dogs are composed of struvite.  Struvite stone formation may be associated with several factors, including alkaline urine, diet, and genetic predisposition.  However, struvite stones most often form following urinary changes resulting from a urinary tract infection.  Specific types of infection in the urinary tract that can cause or contribute to struvite stone formation include staphyloccocal and proteus.  Struvite stones are most often seen in female dogs between the ages of 1 and 8 years of age.

Treatment: Stone dissolution as well as treatment and ongoing management of the urinary tract infection.  The underlying urinary tract infection is generally treated with antibiotics.  The struvite stones can be dissolved with dietary modification, removed surgically, or removed with a technique called "voiding urohydropropulsion." 

Prevention:  Struvite stone formation can in many cases be controlled through diet.  Dogs prone to struvite stones should be: (1) given fresh, clean water; (2) allowed to urinate as frequently as needed; (3) fed a veterinarian-recommended diet formulated to maintain an acidic urine and lower urinary phosphate and magnesium; and (4) monitored for urinary tract infections.

Oxalate:  Calcium oxalate uroliths are the second most prevalent type of bladder stones.  There is thought to be a strong hereditary component to the formation of calcium oxalate stones.  Oxalate uroliths occur most often in male dogs between 5 and 12 years of age.  Because of the structure of the male anatomy, male dogs with oxalate uroliths are prone to urethral obstruction.

Treatment: Calcium oxalate stones cannot be dissolved by diet change; therefore, surgical or laser removal of the stones may be medically necessary.

Prevention: (1) Provide access to fresh, clean water; (2) allow the dog to urinate as frequently as needed; and (3) follow a veterinarian's advice regarding diet and medication appropriate for this condition.  Feeding a calcium-restricted diet to prevent recurrence of calcium oxalate uroliths is a controversial issue.  Calcium restriction may not prevent oxalate urolith formation.  Further, many people feel that the risks associated with feeding canines a reduced calcium diet outweigh any potential benefits.

Other Uroliths: Other types of uroliths that occur less frequently include ammonium urate, cysteine, silica, calcium phosphate, and uroliths composed of miscellaneous other minerals.  Treatment is specific to the type of urolith.