Extremely High Creatine Kinase Activity in Rhabdomyolysis without Acute Kidney Injury

BACKGROUND Elevation of creatine kinase (CK) activity has been shown to be predictive of acute kidney injury (AKI) in rhabdomyolysis. Patients with extremely high CK activity with preserved renal function are uncommon. This report describes a case of non-traumatic rhabdomyolysis, with a markedly elevated CK activity, without associated AKI. CASE REPORT A 22-year-old male presented with severe generalized myalgias and darkened urine for 1 week prior to his admission. The patient presented to the Emergency Department with initial CK activity of >40 000 U/L and a serum creatinine level of 0.77 mg/dL. Urinalysis was positive for myoglobinuria. Serum cystatin C confirmed an estimated glomerular filtration rate of 144 mL/min/1.73 m². Several causes of rhabdomyolysis, including viral infections, Lyme disease, viral hepatitis, hypothyroidism, and cocaine abuse were investigated; however, all were negative. He was given a bolus of 2 liters of normal saline and continued on intravenous normal saline at 250 mL/hour throughout his hospital stay. Urine output remained adequate. We were able to quantify his serum CK activity by dilution method, which revealed a serum CK activity of >150 000 U/L. His CK levels consistently trended down with treatment. CONCLUSIONS An extremely high CK activity in rhabdomyolysis may lead to AKI. However, preserved kidney function is possible. Young age, no concurrent cocaine use, and adequate oral fluid hydration may prevent AKI in rhabdomyolysis. Physicians need to remain vigilant for cases of rhabdomyolysis that have not yet caused renal compromise.