Page 697 - Small Animal Internal Medicine, 6th Edition

CHAPTER 39 Diagnostic Tests for the Urinary System 669

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FIG 39.12 FIG 39.13
Photomicrograph showing numerous rod-shaped bacteria in Photomicrograph of ammonium biurate crystals in urine
urine sediment and a single struvite crystal (lower left). Red sediment (Sedi-Stain, ×400).
blood cells also are present (Sedi-Stain, ×400).

TABLE 39.3

Conditions Associated With Crystalluria
CRYSTAL
TYPE ASSOCIATED CONDITIONS
Struvite Normal
Urinary tract infection with urease-
positive bacteria
Struvite urolithiasis
Plant protein-based diet
Calcium Normal
oxalate Ethylene glycol intoxication
Oxalate urolithiasis
Ammonium Breed-related (e.g., Dalmatian, English FIG 39.14
Photomicrograph showing numerous struvite crystals in urine
biurate Bulldog) sediment (unstained, ×400).
Urate urolithiasis
Liver disease
Portosystemic shunt typically are found in alkaline urine. Characteristic crystals
Cystine Cystinuria also may be found in the urine sediment of animals receiving
Bilirubin Normal in concentrated urine from certain drugs, especially sulfonamides. Bilirubin crystals
dogs (especially males); abnormal may be found in concentrated samples of normal dog urine.
in feline urine Urates are commonly observed in the urine of Dalmatians
Hemolytic disease and may be seen in the urine of animals with liver disease
Liver disease or portosystemic shunts (Fig. 39.13). Struvite crystals may
Posthepatic disease be observed in the urine of cats with idiopathic lower urinary
tract disease, in dogs and cats with struvite urolithiasis, and
in the urine of normal animals (Fig. 39.14). In the presence
urine of dogs and cats and often are of little diagnostic sig- of oliguric AKI, the presence of calcium oxalate crystals (Fig.
nificance (Table 39.3). Struvite, amorphous phosphates, and 39.15) is highly suggestive of ethylene glycol intoxication.
oxalates are examples of crystals that may be found in normal The presence of cystine crystals in urine of dogs and cats is
urine samples. Prolonged storage of urine (24 versus 6 hours) abnormal and suggestive of cystinuria (Fig. 39.16).
and refrigeration can increase the number and size of crys-
tals, especially calcium oxalate, observed in the urine sedi- Miscellaneous
ment. Uric acid, calcium oxalate, and cystine typically are Sperm are commonly found in urine samples from normal
found in acidic urine, whereas struvite (MgNH 4 PO 4 • 6H 2 O, intact male dogs. Rarely, parasite ova of Dioctophyma renale
so-called triple phosphate), calcium phosphate, calcium car- or Capillaria plica or microfilaria of Dirofilaria immitis may
bonate, amorphous phosphate, and ammonium biurate be observed in the urine sediment. Refractile lipid droplets