Reye Syndrome Workup

Updated: Apr 02, 2018
  • Author: Debra L Weiner, MD, PhD; Chief Editor: Kirsten A Bechtel, MD  more...
  • Print

Approach Considerations

Workup to exclude inborn errors of metabolism (IEMs) must be performed and should include evaluation for defects of fatty-acid oxidation, amino and organic acidurias, urea-cycle defects, and disorders of carbohydrate metabolism. Various invasive procedures may be indicated. Computed tomography (CT) of the head may reveal cerebral edema, but the results are usually normal. Electroencephalography (EEG) may reveal slow-wave activity in the early stages and flattened waves in advanced stages. MRI characteristics of Reye syndrome are symmetric thalamic, white matter and basal ganglia lesions, in children with recent history of salycilates or immunosuppressive drugs intake. [9]


Laboratory Studies


An ammonia level as high as 1.5 times normal 24-48 hours after the onset of mental status changes is the most frequent laboratory abnormality. Ammonia tends to peak 56-60 hours after the onset of symptoms. The ammonia level may return to normal in stages 4 and 5.

Liver function tests

Levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) increase to 3 times normal but may return to normal by stages 4 or 5. Bilirubin levels are higher than 2 mg/dL (but usually lower than 3 mg/dL) in 10-15% of patients. If the direct bilirubin level is more than 15% of total or if the total bilirubin level exceeds 3 mg/dL, consider other diagnoses.

Lipase and amylase levels are elevated. The serum bicarbonate level is decreased secondary to vomiting. Blood urea nitrogen (BUN) and creatinine levels are elevated.

Lactic dehydrogenase (LDH) 

LDH may be high or low.


While glucose is usually normal, it may be low, particularly during stage 5 and in children younger than 1 year.

Electrolytes, blood urea nitrogen (BUN), creatinine

Sodium may be low due to syndrome of inappropriate antidiuretic hormone (SIADH) or elevated due to diabetes insipidus (DI). Serum bicarbonate is usually decreased due to vomiting. BUN and creatinine are usually elevated.  Anion gap is usually elevated due to metabolic acidosis.

Coagulation studies

Prothrombin time (PT) and activated partial thromboplastin time (aPTT) are prolonged more than 1.5-fold in more than 50% of patients. Levels of factors I (fibrinogen), II, VII, IX, and X may be low because of the disruption of synthetic activities in the liver. Consumption may also contribute to low levels of coagulation factors. Platelet counts are usually normal.

Fatty acids, amino acids

Levels of free fatty acids and amino acids (eg, glutamine, alanine, and lysine) may be elevated.

Blood gas

Venous blood gas should be obtained to evaluate for metabolic acidosis.


Urine specific gravity is increased; 80% of patients have ketonuria.

Cerebral spinal fluid (CSF)

CSF WBC count, by disease definition, does not exceed 8 cells/µL. Opening pressure is usually normal but may be elevated, particularly in stages 3-5.

Recognize that these derangements are not specific for Reye syndrome and may suggest other etiologies that should be considered.


Invasive Procedures

The following procedures may be helpful for workup, treatment, and monitoring:

  • Vascular access (arterial, central venous, or both)

  • Lumbar puncture if the patient is hemodynamically stable and shows no signs of increased intracranial pressure (ICP) – Opening pressure may or may not be increased; the white blood cell (WBC) count in the cerebrospinal fluid (CSF) is 8/µL or fewer

  • Intubation to maintain airway and ventilation and to manage ICP

  • Nasogastric tube placement to decompress the abdomen

  • Bladder catheterization to monitor urine output

  • Percutaneous liver biopsy (if indicated) to exclude an IEM or toxic liver disease

  • Placement of an intracranial device for ICP monitoring in patients with increased ICP

Coagulopathy must be corrected before invasive procedures are performed.


Imaging Studies

Computed tomography

CT may reveal diffuse cerebral edema but may be normal.

Magnetic resonance imaging (MRI)

There are very few reports of MRI findings of Reye syndrome given the rarity of this condition since MRI has been available. Diffuse cerebral edema and diffusion restriction in thalamic midbrain, cerebral and subcortical white matter, and parasagittal cortex have been reported.


Other Tests

Electroencephalogram (EEG)

In early stages EEG may reveal slow wave activity, in later stages, flattened waves. [19]