14 DO interpret the quantity of crystals in terms of urine specific gravity values. For example, a few struvite crystals observed
in urine with a specific gravity of 1.010 is quantitatively more significant than a few crystals observed in urine with a
specific gravity value of 1.060. On the other hand, a concentrated urine sample is usually more conducive to crystal formation
than an unconcentrated urine sample.
15 DO consider whether the patient is in a postprandial or fasting state when interpreting the significance of crystalluria. Diet-associated
crystalluria is likely enhanced in the postprandial state.
16 DO consider the patient's diet when interpreting the significance of crystalluria because crystalluria may also be influenced
by diet, including water intake. Why? Urine crystal formation that occurs while patients are consuming hospital diets may
be dissimilar to urine crystal formation that occurs when patients are consuming diets fed at home.
17 DO recognize that crystalluria is not synonymous with the presence of uroliths. Crystalluria is often present in absence of
uroliths. Conversely, uroliths can be present without concomitant microscopic crystalluria.
18 DON'T rely on microscopic evaluation of urine crystals as the sole criterion of the mineral composition of uroliths. Only quantitative
analysis can provide definitive information about the mineral composition of the entire urolith. However, interpretation of
crystalluria along with other clinical findings can often allow you to establish a tentative identification of the mineral
composition of uroliths, especially their recently formed outermost layers.
19 DO evaluate the patient for reduction or elimination of crystals by therapy. Absence of crystals provides a useful index of
the efficacy of medical protocols designed to dissolve or prevent uroliths.
20 DO repeat the urinalysis when significant crystalluria is detected in animals with otherwise normal urinary tract function.
Persistent crystalluria usually represents a greater risk for urolith formation than transient crystalluria.
21 DO avoid "always or never" and "all or none" interpretations regarding the clinical significance of crystalluria.