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Rhabdomyolysis is the destruction of skeletal muscle, caused by any mechanism that results in injury to myocytes and their membranes. Table 51-1 lists commonly recognized conditions associated with rhabdomyolysis. In general, the most common causes of rhabdomyolysis in adults are alcohol and drugs of abuse, followed by medications, muscle diseases, trauma, neuroleptic malignant syndrome, seizures, immobility, infection, strenuous physical activity, and heat-related illness. Multiple causes are present in more than half of patients. In children, rhabdomyolysis is less common and is thought to be more benign.
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Symptoms are usually acute in onset and include myalgias, stiffness, weakness, malaise, low-grade fever, and dark (usually brown) urine. Nausea, vomiting, abdominal pain, and tachycardia can occur in severe rhabdomyolysis. Muscle symptoms, however, may be present in only half of cases. Some patients may present with complications of rhabdomyolysis such as acute renal failure, metabolic derangements, disseminated intravascular coagulation, and mechanical complications (e.g., compartment syndrome or peripheral neuropathy) (Table 51-2).
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Acute rhabdomyolysis may be present without any of these signs or symptoms and with normal findings on physical examination. For this reason, diagnosis is often made from a significant history, an elevated serum creatine kinase level or the presence of dark urine on routine laboratory testing.
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DIAGNOSIS AND DIFFERENTIAL
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An elevated serum creatine kinase is the most sensitive and reliable indicator of muscle injury. Diagnosis requires a fivefold or greater increase above the upper threshold of normal serum creatine kinase level in the absence of cardiac or brain injury. Persistently elevated levels ...