Page 1200 - Clinical Small Animal Internal Medicine

1138 Section 10 Renal and Genitourinary Disease

Protocol for Medical Management ● Avoidance of calcium‐containing supplements in at‐
VetBooks.ir and Prevention of Individual Urolith Types ● Reduction in foods rich in oxalate precursors.
risk patients.
Calcium Oxalate Uroliths
Dissolution of Calcium Oxalate Uroliths Examples of these include chocolate, nuts, beans,
At present, calcium oxalate stones cannot be dissolved sweet potatoes, wheatgerm, spinach, rhubarb. For a
through medical (nutritional) means in dogs and cats. As complete list of the oxalate content in foods, please
such, removal or bypass of these uroliths by different visit the Oxalosis and Hyperoxaluria Foundation web­
interventional methods is recommended. As upper uri­ site: www.ohf.org.
nary tract stones in cats are predominantly composed of In dogs, the diets recommended to achieve the above
calcium oxalate (>98%), medical dissolution is also not goals are those that have undergone specific urinary test­
recommended in these patients.
ing (i.e., CORI, RSS, Activity Product Ratio) to reduce
risk of calcium oxalate formation. Examples of these
Follow‐Up and Prevention of Calcium Oxalate Uroliths diets include Hill’s c/d, Purina St/Ox, and Royal Canin
Dietary therapy has been recommended to help prevent S/O. Unfortunately, the ideal diet to prevent calcium
recurrence of calcium oxalate stones. Nutritional strate­ oxalate urolith recurrence remains unknown.
gies to aid prevention of calcium oxalate stones in cats or Despite diet modification, recurrence in animals with
dogs primarily focus on increasing water intake via feed­ CaOx is high: 33% at two years in cats and up to 57% at
ing canned or wet food or by adding water to dry food. three years in dogs. If calcium oxalate uroliths recur
These techniques help to increase dilution of urine and despite dietary therapy, the use of medications such as
flush crystals from the urinary tract, and one study thiazide diuretics or potassium citrate may benefit spe­
showed that feeding canned food to a group of dogs cific patients.
decreased their risk of calcium oxalate compared to Potassium citrate supplementation has been shown to
feeding a dry diet. reduce recurrence of calcium oxalate uroliths in humans.
Medical management that is believed to prevent recur­
rence of calcium oxalate urolithiasis includes the follow­ In veterinary patients, there are conflicting opinions on
the utility of potassium citrate for prevention of calcium
ing factors.
oxalate urolithiasis. In normal dogs, potassium citrate
Increased water content of food (>75% water: high supplementation did not significantly increase the mean
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moisture). citrate excretion, although in three miniature schnauzers
Avoidance of dietary urinary acidification (pH <6.25 supplementation did increase urinary citrate excretion
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cats and <6.6. dogs). and lower relative calcium oxalate supersaturation. In
Correction of underlying hypercalcemia. In cats with another study, potassium citrate did not increase mean
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recurrent CaOx stones and idiopathic hypercalcemia, urinary citrate concentration but did cause a dose‐
there may be a benefit to feeding a high‐fiber diet in dependent increase in urine pH. If calcium oxalate crys­
association with potassium citrate therapy. talluria is persistent or calcium oxalate uroliths recur,
Dietary sodium increase. Controversial at this time. potassium citrate is commonly recommended to achieve
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Feeding high‐sodium diets (3.5 g/1000 kcal) is not a a urine pH of 6.5–7.0 using a dose of 150 mg/kg PO q24h.
substitute for increased dietary moisture, as had been The serum potassium should be initially monitored
previously thought, and any benefit of dietary increase monthly during potassium citrate supplementation and
in salt is believed to be short‐lived. the dose reduced if hyperkalemia occurs.
Management with potassium citrate in cats and dogs Thiazide diuretics are proven to reduce the recurrence
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with persistence of acidic urine, and consideration of calcium oxalate urolithiasis in humans by reducing
of thiazide diuretics if recurrence despite other urinary calcium excretion. However, there are conflict­
interventions. ing results for dogs, and in normal dogs, administration
Dietary protein restriction. At present, the recommen­ of chlorothiazide did not reduce urinary calcium excre­
●
dation to restrict dietary protein in these patients is tion. In contrast, administration of hydrochlorothiazide
controversial and it is very difficult to reduce dietary decreased urinary calcium excretion and urine calcium
protein without concurrent dietary phosphorus reduc­ concentration in dogs with calcium oxalate urolithiasis.
tion. Unfortunately, lower phosphorus has been asso­ Reduction in urinary calcium was greatest in dogs with
ciated with a higher risk of calcium oxalate uroliths. the highest pretreatment urine calcium concentrations
This is due to low diet phosphorus leading to increased when combined with using Hill’s Prescription Diet u/d.
intestinal absorption of calcium and increased calci­ As thiazide diuretics contribute to urine acidification,
triol production, which then leads to further calcium concomitant administration of potassium citrate may be
gastrointestinal absorption and calciuresis. recommended. Hydrochlorothiazide (2 mg/kg PO q12h)