Urinary SO (SO stands for "struvite and oxalate") is a type of veterinary diet specifically formulated to help dissolve struvite stones in dogs and cats. This type of diet works by reducing the levels of certain minerals in the urine, which can help prevent the formation of new stones and dissolve existing ones. Struvite stones are a common type of urinary stone in dogs and cats, and they are composed primarily of magnesium, ammonium, and phosphate. Urinary SO is formulated to reduce the levels of these minerals in the urine, which can help dissolve existing struvite stones over time. However, Urinary SO is not effective in dissolving all types of urinary stones. For example, it is not effective in dissolving calcium oxalate stones, which are different types of urinary stones that can also occur in dogs and cats.