When cherry colored urine is observed, which parameter best indicates rhabdomyolysis?

• A. CPK level
• B. Blood urea nitrogen
• C. Creatinine clearance
• D. Serum albumin

Answer: (A)

When muscle tissue breaks down as in rhabdomyolysis, myoglobin spills into the blood and urine, producing dark or cherry-colored urine. The most informative test for this condition is the creatine phosphokinase (CPK) level because CK is released in large amounts from damaged skeletal muscle and directly reflects the extent of muscle injury. CK elevations correlate with rhabdomyolysis and are more specific to muscle breakdown than other tests.

BUN and creatinine clearance mainly assess kidney function and can be affected by hydration status or kidney injury, but they don’t specifically indicate muscle damage. Serum albumin is a general protein marker and does not reflect muscle breakdown.