The diagnosis of acute mercury toxicity is partly clinical, based on symptoms of respiratory distress. Laboratory evaluation of acute mercury poisoning should also include a complete blood count and differential, serum electrolytes, glucose, liver, and renal function tests, and urinalysis. Obtain hourly intake/output and urine pH in severely ill patients when renal perfusion is in question. Pulse oximetry might yield insufficient information to carefully monitor impending pneumonitis, ARDS, or respiratory failure. Chest radiography and serial ABG measurements are recommended for severe inhalation exposures.
Blood and urine mercury levels are useful to confirm exposure but there is no definite correlation between blood and urine mercury levels and degree of mercury toxicity. Blood mercury level confirms whether the exposure was recent, because the initial half-life for the elimination of blood mercury is 3 days. Urinary mercury levels indicate the total mercury body burden since mercury is largely excreted by the kidneys. The half-life of elimination for whole body mercury is 60 to 90 days. Urinary mercury levels are generally below 10 μg/L. Blood mercury levels are generally less than 40 μg/L and should not exceed 50 μg/L. Long-term exposure to mercury can be estimated from levels in hair.
If large-volume ingestion (more than the contents of a thermometer) is suspected, abdominal radiographs should be ordered to detect and follow the transit of any mercury (which is radiopaque) in the gastrointestinal tract. Neuropsychiatric testing, nerve conduction studies, and urine assays for N-acetyl-B-D-glucosaminidase and β2-microglobulin have been used to assess delayed and chronic nervous system and renal toxicity.