Which laboratory finding is most concerning for rhabdomyolysis?

• A. Decreased creatine kinase
• B. Normal potassium
• C. Normal urinalysis
• D. Elevated creatine kinase

Answer: (D)

Rhabdomyolysis causes muscle cells to release enzymes and other contents into the bloodstream, with creatine kinase (CK) being a key enzyme released from skeletal muscle. Elevation of CK directly reflects the extent of muscle injury and is the most informative marker for diagnosing rhabdomyolysis and monitoring its severity. High CK levels help anticipate complications such as acute kidney injury from myoglobin and electrolyte disturbances, guiding urgent management. A lower or normal CK would not indicate the muscle breakdown happening, and normal potassium or a normal urinalysis could miss the ongoing injury and its risks. So, an elevated CK best captures the presence and seriousness of rhabdomyolysis.