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Canine Silica
Urolith
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Early reports
indicated a predominance of silica stones in German Shepherds, but many
breeds have now been implicated.
Available
clinical data provides a strong link between canine silica uroliths and
dietary ingredients. Silica uroliths may occur in dogs with a pica for
eating soil or in
dogs eating diets high in cereal grains containing silicates such as
corn gluten and soybean hulls. More than 95% of the silica stones
reported in canines occur in male dogs. Urethral obstruction in
males is the most common presenting problem,
but signs similar to those associated with other types of uroliths also
may be noted. The mean age at occurrence is 6 yr. The stones are
usually multiple and develop in the bladder and urethra. Silica
uroliths are radio-opaque. They frequently, but not always, have a
characteristic “jack-stone” appearance. This is because their most
typical form or
habit resembles the children's game of jacks.
Identification
requires
spectrographic analysis and cannot be made with kits for qualitative
stone analysis.
The role of diet
in spontaneously occurring silica urolithiasis has not
been determined, although plants are often an abundant source of
silica. If the diet of an affected dog is known to be high in silica,
or if silica urolithiasis has been recurrent, a dietary change should
be recommended. Only general management principles can be suggested for
silicate urolithiasis. Additional salt and/or water should be added to
the diet to induce diuresis and to lower the urine solute
concentration. When present, urinary tract infections should be
eliminated. Diets high in plant proteins should be avoided.
In
describing gross characteristics of this urolith type, silica stones
are sometimes called "jackstones" because their most typical form or
habit resembles the children's game of jacks.
Appropriate
diagnostic studies are needed to identify location and size of
uroliths, or post-surgical radiographs are taken to determine efficacy
of
surgical removal. A complete urinalysis and urine culture is also
required.
Effective
medical protocols to induce dissolution of canine silica
uroliths have not yet been developed. Prevention of these stones
involves taking steps to minimize risk factors.
1. Diets
containing substantial plant proteins, and
especially avoid those containing soybean hulls or corn gluten feed are
to be avoided. Moisture should be added to the diet to enhance
diuresis
2. Since calcium
oxalate
is sometimes detected in silica uroliths, we do not recommend addition
of sodium chloride to the diet to stimulate thirst and diuresis.
Excessive sodium has been shown to enhance calcium excretion in urine.
3. Avoid efforts
to deliberately acidify the urine.
4. Monitor for,
and if necessary treat urinary tract infections with appropriate
antimicrobial agents.
