ATN
The tubular vacuolization and tubular dilation here is a result of the toxic effect of ethylene glycol poisoning. This is representative of acute tubular necrosis (ATN), which has many causes. ATN resulting from toxins usually has diffuse tubular involvement, whereas ATN resulting from ischemia (as in profound hypotension from cardiac failure) has patchy tubular involvement.

Another example of toxic ATN is shown below. Skeletal muscle injury may trigger rhabdomyolysis that can be detected by urine dipstick analysis as positive blood, but no red blood cells on urine microscopic examination. This is explained by the presence of myoglobin, which gives the urine a dark brown appearance. Myoglobin is protein, accounting for the 1+ dipstick measurement for protein. With rhabdomyolysis, the serum creatine kinase will be elevated.

Macroscopic Urinalysis:

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Leukocyte esterase
Nitrite
pH
Protein
Blood
Specific gravity
Ketones
Glucose
Bilirubin
CharacteristicResult
ColorDark brown
AppearanceSlightly Cloudy
Leukocyte EsteraseNeg
NitriteNeg
pH6.5
Protein1+
Blood3+
Specific Gravity1.015
KetonesNeg
GlucoseNeg
BilirubinNeg

Microscopic Urinalysis:

CharacteristicResult
WBC/hpf <2/hpf
RBC/hpf None
Casts None
Other Few hyaline casts