The approach to the evaluation of rhabdomyolysis is as follows:

• Minimum Evaluation
  • Etiology certain:
    • CBC (complete blood count)
    • CK
    • Chemistries
    • Liver function tests
    • Urine pH
  • Consider looking for hypothyroidism and sickle cell trait.
• Extensive Evaluation:
  • If etiology is uncertain, the following labs can be checked:
    • Thyroid stimulating hormone
    • Erythrocyte glycolytic enzymes
    • CPT I/II in leukocytes
    • Serum carnitine
    • Organic acids in urine.

• Urinalysis
  • Blood (+)
  • No red blood cells on microscopy. This situation is either hemoglobin in the urine or myoglobin. The serum will be pink with hemoglobinuria.
• Serum Markers
  • Elevated serum creatinine kinase
    • CK elevation: Generally accepted > 5 times normal. Corresponds to about 200g of muscle.
    • Begins to rise 2-12 hrs after onset. Peaks 1-3 days in. Declines 3-5 days after the process stops.
  • Myoglobin
    • Myoglobin: Starts earlier than CK but clears faster, so serum and urine myoglobin useful early in course of the disease. Myoglobin is eventually urinated and/or converted to bilirubin.
    • All myoglobinuria is caused by rhabdomyolysis, but not all rhabdomyolysis causes myoglobinuria. Urine changes color when > 1mg/ml.
  • LDH (lactic dehydrogenase)