for development of calcium oxalate uroliths increases. By feeding proper amounts of calcium and potassium we avoid this issue, which is especially common in male cats. Diagnosis When symptoms indicate bladder stones, the first step is usually to take an x-ray. Most types of stones will appear readily in an x-ray, urate and occasionally cystine stones being the most common exceptions. Stones smaller than three millimeters may not be visible. Ultrasonography is also useful for identifying bladder stones. Crystals identified in a urinalysis may help identify the stones, but analysis of the stones is necessary for identification of the complete chemical composition. Struvite stones Struvite stones are also known as magnesium ammonium phosphate stones due to their chemical composition - MgNH4PO4·6H2O. Often there is a small amount of calcium phosphate present. They form at a neutral to alkaline pH of the urine. Bacterial infections contribute to their formation by increasing the pH of the urine through the urease enzyme in dogs. More than 90 percent of dogs with struvite stones have an associated urease-producing bacterial infection in the urinary tract, but in cats struvite stones usually form in sterile urine. The appearance of the stones vary from large solitary stones to multiple smaller stones. They can assume the shape of the bladder or urethra. Dissolution of the struvite stones depends on acidification of the urine through diet or urinary acidifiers. Special diets for dissolution also have reduced protein, phosphorus, and magnesium, as well as increased salt to increase water consumption and dilute the urine. The diet needs to be fed exclusively, but it can only be fed for a few months total due to potential side effects. Contraindications to this diet include heart failure, liver failure, kidney failure, pancreatitis, hypertension (high blood pressure), and hypoalbuminemia (low serum albumin). Prevention of struvite stones is with a similar diet with milder restrictions. Certain dog breeds are predisposed to struvite stones, including Miniature Schnauzers, Bichon Frises, and Cocker Spaniels. They are the most commonly reported bladder stone in female dogs and in ferrets (pregnant ferrets may be especially predisposed). For frequency in cats, see below. Calcium oxalate stones Calcium oxalate stones form in an acidic to neutral urine. Two types naturally occur, calcium oxalate monohydrate, or whewellite (CaC2O4·H2O), and calcium oxalate dihydrate, or weddellite (CaC2O4·2H2O). Their appearance can be rough, smooth, spiculated (needle-like), or jackstone. Calcium oxalate stones form more readily in animals