Rhabdomyolysis Clinical Presentation

Updated: Oct 14, 2018
  • Author: Marietta Morales De Guzman, MD; Chief Editor: Lawrence K Jung, MD  more...
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Presentation

History

The classic triad of rhabdomyolysis comprises the following:

  • Myalgias

  • Generalized weakness

  • Darkened urine

In practice, however, the presentation of rhabdomyolysis varies considerably. The classic triad is actually seen in only about 50% of adult patients, and it may be even less common in children. [11] Additional nonspecific symptoms include fevers, unusual or severe fatigue,  nausea, and vomiting.

In most cases, the history reflects the inciting cause (eg, alcohol use and resultant unresponsiveness, agitation and illicit drug use, use of prescribed medications, or heatstroke). [62, 56, 41, 40] In children, infection and trauma are the most common causes. [6] Caregivers in contact with the patient before hospitalization may provide useful information about how the patient was found or what he or she had been doing most recently. Obtain information about prolonged immobilization from the patient (if possible) or an informant.

In some patients, the history is nonspecific and therefore is unreliable for diagnostic purposes.

Clinicians may need to investigate metabolic causes (eg, diabetic ketoacidosis and diabetes mellitus) and other nontraumatic causes (eg, congenital defects, viral infection, anesthesia use, physical exertion, and seizure disorder). Inflammatory myopathies of recent and acute onset may manifest as rhabdomyolysis. [11]

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Physical Examination

The initial physical examination findings may be nonspecific (especially in pediatric populations). [6, 11]

Patients may have muscular pain and tenderness, decreased muscle strength, soft tissue swelling, and skin changes consistent with pressure necrosis. The most commonly involved muscle groups in adults include the calves and the lower back. Back, chest, and calf pain often mimics other common conditions such as deep vein thrombosis or angina.

On the whole, focal or diffuse skeletal muscle swelling is rare. In one series, only 5% of the patients presented with muscle edema. Tense and tender muscle compartments suggest compartment syndrome; peripheral pulses that are within reference range do not rule out compartment syndrome, because loss of distal pulses is a very late sign.

Hyperthermia, hypothermia, and electrical injuries are known to cause rhabdomyolysis and can often be detected upon physical examination. Examine for any crush injuries or deformities in long bones if orthopedic injures after trauma are suspected.

The presence of rhabdomyolysis should not be discounted if the patient lacks classic history, physical examination findings, or both. If evolving rhabdomyolysis is suspected based on the clinical scenario, an appropriate laboratory evaluation should be performed to diagnose muscle damage and organ dysfunction. [1]

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Complications

Electrolyte abnormalities are prominent features of rhabdomyolysis. Hyperphosphatemia, hyperkalemia, hypocalcemia (early), hypercalcemia (late) hyperuricemia, and hypoalbuminemia have been described. [4, 14]

Hyperkalemia may be a result of both muscle injury and renal insufficiency or failure. This abnormality may cause life-threatening arrhythmias and should be immediately addressed.

Hypocalcemia is another common metabolic abnormality, resulting from deposition of calcium phosphate. It may also be due to a decreased level of 1,25-dihydroxycholecalciferol in patients with renal failure. Severe hypocalcemia may lead to cardiac arrhythmias, muscular contractions, and seizures. These events may further damage affected muscles. Late findings of hypercalcemia may be related of Ca leakage from damaged muscles and poor clearance if the case is complicated by kidney injury.

Hypoalbuminemia results from proteinuria and direct leakage of protein, whereas hyperuricemia is caused by direct damage to muscle and may contribute to renal tubular damage.

Compartment syndrome may be either a complication of or the inciting cause of rhabdomyolysis. If muscle injury has occurred, measure compartment pressures; if the pressure is higher than 30 mm Hg, fasciotomy is indicated. [1]

Acute kidney injury (AKI) occurs in 17-35% of adult patients [65] and in 5-42% in 2 pediatric case series. [6] Etiologies of AKI may be related to hypovolemia, vasoconstriction, and myoglobin toxicity.

AKI and disseminated intravascular coagulation (DIC, a late complication) are the most severe complications of rhabdomyolysis, often developing 12-72 hours after initial muscle damage. AKI may account for as many as 35% of adult cases. This figure may be as low as 5% in children. [6, 62] Rhabdomyolysis may account for 7-10% of acute kidney injuries in the United States. [3, 62]

Renal failure may also develop in patients treated with optimal measures. Mechanisms of renal injury are multifactorial and may include renal vasoconstriction, intraluminal myoglobin cast formation, and heme-protein cellular toxicity. Myoglobin and hemoglobin toxic effect on the glomerulus are enhanced by aciduria and hypovolemia.

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