iSEDIMENT

What is the diagnosis?

Quadricep muscle biopsy

Urine bag

________
Answer to iSediment of 11/21/11 is ethylene glycol toxicity, answer D

A 30-year-old white male was brought to the emergency department (ED) following suicidal ingestion of ¼ oz. of cocaine and an unknown fluid. Clinical features included agitation, pinpoint pupils and hypertension (blood pressure181/104 mmHg). Other vital signs were as follows; heart rate is 96 beat per minute, respiratory rate is 12 cycles per minute, temperature is 100.8⁰ F (38.2 deg C), his oxygen saturation is 97 % on room air. His laboratory tests in the ED (Table) showed a metabolic acidosis with an anion gap of 26 and an osmolal gap of 32. The arterial blood gas on room air was pH 7.20, PCO2 21 mmHg, PO2 108 mmHg. Urine sediment showed crystals and renal tubular epithelial cells (Fig. 1-3). Renal ultrasound showed that the kidneys were normal in size and appearance with no stones or hydronephrosis and normal parenchymal echogenicity. His EKG showed peaked Ts.

The unknown fluid that this patient ingested is most likely to be (choose one):

A. Methanol

B. Ethanol

C. Isopropanol

D. Ethylene glycol

E. Paraquat

Fig.2 Urine sediment using polarized light

Fig.1 Light microscopy of urine sediment x40

Fig. 3 Urine sediment viewed using immuofluorescent  microscope x 40

Explanation

The clinical diagnosis is ethylene glycol and cocaine toxicity. The blood ethylene glycol level was 40 mg/dL. He was given charcoal. Fomepizole; 10 mg/kg IV in 100 cc D5 over 30 minutes Q12H for 4 doses was administered. He was also dialyzed. 

The major use of ethylene glycol is as a coolant or antifreeze in hydraulic systems of cars and personal computers. It is also used as a deicing fluid for windshields and aircraft, and in the manufacture of plastics. The "parent alcohol" ethylene glycol is colorless and has a sweet taste. Direct effects of ethylene glycol ingestion are mainly central nervous system sedation. However, the ethylene glycol metabolites glycolate, glyoxylate and oxalate can cause renal failure following large ingestions (approximately 20 mg/dL). 

Ethylene glycol is rapidly and completely absorbed after oral ingestion with peak serum concentration within one to two hours. Identifying the source and nature of the exposure is crucial. This is ideally done by retrieving the original container and consulting product databases. It is important to clarify when the ingestion occurred, whether ethanol was also ingested, and the intent of the exposure (whether accidental, suicidal or homicidal). Ingestion of approximately 1 g/kg of either methanol or ethylene glycol is generally considered lethal.

Few conditions other than ethylene glycol intoxication present with a profound metabolic acidosis (serum bicarbonate less than 8 meq/L) and most of these conditions present in a characteristic fashion with a high serum lactate (e.g,, methanol intoxication, status epilepticus, profound shock and ischemic bowel). Direct testing of toxic alcohols is the preferred diagnostic test when available. 

The osmolal gap can be used to estimate the serum level of ethylene glycol by applying the following conversion factor 6.2 (calculated by taking the molecular weight of ethylene glycol of 62 and dividing by 10 (based on the chemical formula of C2H6O2 or 16*2+1*6+12*2). An easy screening test is to shine a Wood lamp (UV light) on a sample of urine from the patient early in the clinical presentation. Sodium fluorescein is frequently added to commercial antifreeze preparations as a colorant to facilitate detection of a leak in the hydraulic or cooling system. Thus, a Wood lamp or a fluorescent microscope can be used as an adjunctive screening test in the diagnosis of ethylene glycol poisoning. In the case presentation herein a green-colored glow was observed using a fluorescent microscope. 

Examination of the urine for calcium oxalate crystals is frequently performed in patients with possible ethylene glycol poisoning. Two types of calcium oxalate crystals may be seen: needle-shaped monohydrate crystals, which may be misread as hippurate crystals, and envelope-shaped dehydrate crystals. However, it is important to note that the formation of calcium oxalate crystals is not dependent upon the urine pH.

(Youssef Farag, MD developed this case)