Page 888 - Small Animal Clinical Nutrition 5th Edition

Canine Silica Urolithiasis 919

uroliths. Voiding urohydropropulsion may be used to remove
Table 44-2. Levels of key nutritional factors in selected
VetBooks.ir 1993). Lithotripsy may be considered to remove urethroliths. commercial foods used to minimize recurrence of silica
small urocystoliths (Figure 38-5 and Table 38-7) (Lulich et al,
uroliths in dogs compared to recommended levels.*
Litholytic foods that do not contain large quantities of plant
ingredients and that induce diuresis may prevent further Dry food Protein (%) Urinary pH**
Recommended levels 10-18 7.1-7.7
growth of silica uroliths. Hill’s Prescription Diet u/d Canine 11.2 7.70
At this time, our recommendations include change of diet, Moist food
Hill’s Prescription Diet u/d Canine 13.3 7.40
augmentation of urine volume and consideration of altering
urinary pH (Table 44-1) (Osborne et al, 1986; Osborne et al, *Manufacturer’s published values; protein expressed as % dry
1999). matter; when possible recommend moist foods; where possible,
check the ingredient panel of the product label and avoid foods
that list corn gluten feed, rice hulls or soybean hulls.
Assess and Select the Food **Protocols for measuring urinary pH may vary.
Although the role of food in the genesis of canine silica uroliths
is still somewhat speculative, it seems reasonable to recommend
that food(s) of affected patients be changed, especially if the Besides offering moist foods, there are several additional
problem is recurrent. Although empirical, this maneuver is ways to facilitate increased water intake. These include: 1) En-
unlikely to be harmful and may be helpful. Based on the as- suring multiple water bowls are available in prominent locations
sumption that the primary source of excessive silica in foods is in the dog’s environment; this may mean providing several
vegetable in origin, selection of a food with reduced quantities bowls outside in a large enclosure or a bowl on each level of the
of specific vegetable protein and other plant-based ingredients house. 2) Bowls should be clean and, if possible, kept full of
is recommended. Our empirical experience with this method of fresh water. 3) Small amounts of flavoring substances (e.g., salt-
prevention has been favorable. Table 44-2 lists selected veteri- free bouillon) can be added to water sources to increase con-
nary therapeutic foods that can be considered for prevention of sumption. 4) Ice cubes can be offered as treats or snacks. 5) If a
silica urolithiasis and compares their key nutritional factor con- dry food is selected, advise the client to add liberal quantities of
tent to the recommended levels. Select the food that is most water; however, as with moist foods left at room temperature
similar to the key nutritional factor profile. Because these foods for too long, be aware that there are also potential food safety
are intended for long-term feeding, they should also be issues that might arise from leaving moistened dry foods out for
approved by the Association of American Feed Control prolonged intervals (Chapter 11).
Officials (AAFCO), or some other credible regulatory agency. If the patient has a normal body condition score (BCS 2.5/5
Dogs consuming dry foods may be at greater risk for urolithia- to 3.5/5), the amount of the previous food being fed was prob-
sis than dogs consuming moist foods. Dry foods are often asso- ably appropriate. On an energy basis, a similar amount of the
ciated with higher urine concentrations of urolith constituents new food would be a good starting point.
(in the case of silica urolithiasis, more plant origin ingredients) Oral administration of sodium chloride has been a favored
and more concentrated urine. Therefore, when possible, moist empirical method to induce diuresis in dogs with uroliths.
foods should be selected. However, the use of sodium chloride to promote diuresis in
dogs that form silica uroliths cannot be routinely recommend-
Assess and Determine the Feeding Method ed without evidence of safety and efficacy because of the unpre-
A few dogs with silica uroliths have a history of pica and dictable but marked occurrence of calcium oxalate in silica
coprophagia associated with consumption of dirt and/or com- uroliths and because orally administered sodium chloride is
post in one form or another. The relationship of the onset of associated with hypercalciuria.
pica with the diet history should be investigated with the goal
of correcting this problem. ADJUNCTIVE MEDICAL
Transitioning a patient from the current food to a new food MANAGEMENT
selected for the prevention of silica urolithiasis should be done
gradually over a period of a few days. Begin the transition by Urine Alkalinizing Agents
feeding 75% of the current food and 25% of the new food on Silica is apparently less soluble in acidic than alkaline water, and
Day 1. On Day 2, feed half of each food. On Day 3, feed 75% currently available information suggests that silica is less solu-
new food and 25% old food. By Day 4 or 5, feed only the new ble in acidic than alkaline biologic environments. It is notewor-
food. thy that the urinary pH of eight non-infected dogs with silica
Because moist foods tend to increase water intake and pro- uroliths was acidic to neutral at the time of diagnosis (mean =
duce a less concentrated urine, recommend the client feed spe- 6.0; range = 5.0 to 7.0). Whether or not alkalinization of urine
cific amounts (meal fed) two to three times per day rather than is beneficial in increasing the solubility of silica or silicates in
free-choice feeding. Moist foods can spoil if left at room tem- urine is unknown. Likewise, the effects of orally administered
perature for several hours (Chapter 11). Opened containers of alkalinizing agents (e.g., sodium bicarbonate) on the absorba-
moist foods should be refrigerated and the feeding bowl should bility of silica from the gastrointestinal tract have not been eval-
be kept clean. uated. Nonetheless, it seems prudent to recommend that efforts