Ethylene glycol is a colorless sweet tasting solvent which is used in antifreeze solutions. It is nontoxic
itself but is converted to toxic metabolites in the liver:
Glycolic acid (->glycolate anion) is the major contributor to the often severe high anion gap acidosis that develops
Oxalic acid(->oxalate anion) is one of the final metabolic products which is excreted in the urine. Precipitation of calcium
oxalate crystals in the kidney causes renal failure if a sufficient dose has been ingested.
Fig: Metabolism of Ethylene Glycol
If untreated, ingestion of only 30 to 60 mls may be sufficient to cause permanent organ damage or death.
The osmolar gapmay be raised (to > 10) early in
the course but this is variable.
of calcium oxalate crystals in the urine is often stated to
be a useful guide but this is wrong. Certainly. these crystals have a characteristic appearance
(lsee figure below) and a urinanalysis will
easily detect them. The problem is
that oxalate crystals in urine are generally very common
(80% of specimens) and their presence alone
means nothing for a diagnosis of ethylene glycol ingestion.
Oddly, cases of ethylene glycol ingestion have also been
reported without oxalate crystals in the urine.There is also no point in differentiating between the
monohydrate and the dihydrate crystals.
Fig: Calcium dihydrate crystals in urine - the ones with the 'folded envelope' appearance
Toxicity is usually considered as occurring in 3 stages: intoxication, cardiorespiratory changes
and renal toxicity (see below)