Page 296 - Problem-Based Feline Medicine

288 PART 5 CAT WITH ACUTE ILLNESS

A hemogram typically reveals hemoconcentration and
Differential diagnosis
a stress leukogram.
Both ethylene glycol and lily intoxication cause acute
A serum biochemistry profile will reveal decreased
depression and acute renal failure. The laboratory fea-
bicarbonate (total CO ) and an increased anion gap.
2 tures of lily poisoning have not been as well character-
Blood gases, if available, will reveal severe metabolic
ized as those of ethylene glycol poisoning therefore it is
acidosis with or without partial respiratory compensa-
difficult to use these to differentiate the two poisonings.
tion. Measured osmolality, if available, will be
Ethylene glycol poisoning is more likely in outdoor
increased in parallel with ethylene glycol concentra-
cats and lily poisoning in indoor cats. Vomiting is
tion, resulting in an increased osmolal gap. Other vari-
more consistent in lily poisoning and there is evidence
able findings are hyperglycemia (stress and reduced
of plants being chewed. Detectable serum or urine con-
metabolism by aldehydes), hypocalcemia (chelation
centrations of ethylene glycol, oxalate crystalluria,
by oxalic acid), and hypophosphatemia (binding by
and oxalates on kidney biopsy are diagnostic for
rust-inhibitors in antifreeze). In the later stage of poi-
ethylene glycol poisoning. If these findings are absent,
soning serum chemistry findings are typical of acute
other causes of acute renal failure must be ruled out.
renal failure.
● Both cats with pancreatitis and cats with acute
Urinalysis will reveal persistent isosthenuria to mini- ethylene glycol poisoning may have acute depression
mally concentrated urine and aciduria within 3 hours with or without vomiting, but cats with acute ethylene
of ingestion. Oxalate crystals are usually present at glycol poisoning will be isosthenuric, while cats with
some point during the acute phase of intoxication, and acute pancreatitis should have well-concentrated
may appear as early as 3 hours. Glucosuria and pro- urine. Azotemia, metabolic acidosis, increased anion
teinuria may be present. A Wood’s lamp may be used gap and increased osmolal gap will be more severe
in an effort to detect fluorescence from fluorescein in than in pancreatitis. Definitive diagnosis relies on
stomach contents and on the muzzle and paws. measuring ethylene glycol in serum or urine or seeing
However numerous products contain fluorescents and oxalate crystals in urine or a kidney biopsy.
absence of fluorescence does not rule-out exposure, so ● Both ethylene glycol poisoning and diabetic ketoaci-
the diagnostic utility of fluorescence may be limited. dosis may cause acute depression, polyuria, vomit-
Similarly examination of urine for fluorescence is ing, dehydration, hyperglycemia, azotemia, increased
likely of limited values as cat’s urine normally fluo- anion gap metabolic acidosis, and increased osmolal-
resces and a potential increase in fluorescence from a ity. The former is confirmed by detecting ethylene
small amount of excreted fluorescein may be difficult glycol in serum or oxalate crystals and the latter by
to detect. detecting ketones in the blood or urine. Ethylene
glycol poisoning invariably causes acute renal failure
Definitive diagnosis can be made by measuring ethyl-
(unless treated within 3 hours), while acute renal fail-
ene glycol in serum or urine, but cats are very
ure is an uncommon complication of diabetic ketoaci-
sensitive to ethylene glycol poisoning and may
dosis, although cats with diabetic ketoacidosis may
develop signs at concentrations below that detected
have concurrent chronic renal failure.
by the assays. Serum is preferred because concentra-
tion of the poison is higher than in urine. Ethylene Ethanol ingestion may cause depression, polyuria,
glycol is usually not detectable in serum or urine after ataxia and increased osmolality. Diagnosis relies on
72 hours. Propylene glycol (present in diazepam history of ingestion and measurement of ethanol in
injection) causes a false positive reaction in some the serum.
assays.
Certain abnormalities in the acute phase of ethylene
Ultrasound may reveal hyperechoic renal cortices. The glycol poisoning (depression, tremors, hypocalcemia)
kidney may feel very firm when advancing a percuta- may resemble acute hypoparathyroidism. Other his-
neous biopsy needle. torical and physical abnormalities, and the presence of
● Kidney biopsy will reveal acute tubular necrosis, hyperphosphatemia in the latter, will distinguish the
with the presence of oxalate crystals. two.