Rhabdomyolysis

Last revised by Rohit Sharma on 1 Mar 2024

Rhabdomyolysis describes the breakdown of striated muscles with the release of intracellular contents and represents a severe muscle injury. MRI is the imaging modality of choice. Rhabdomyolysis is potentially life-threatening although recovery is excellent with early treatment.

Symptoms and signs are varied, but a classic triad of muscle pain, weakness, and dark urine are described. 

Most common causes reported in Western adult populations are trauma/crush injury, exercise, cocaine use and immobilization. However, the range of causes is wide 12,13

  • non-traumatic

    • infectious

      • infectious myositis

      • bacteria (mycoplasma, clostridia, legionella)

      • viruses (enterovirus, influenza, herpes simplex)

    • electrolyte abnormalities

      • hypokalemia, hypocalcemia, hypophosphatemia

    • immune-mediated

    • endocrine

    • xenobiotics

      • ethanol, HMG-CoA reductase inhibitors (statins), fibrates

      • amphetamines, cocaine, synthetic cannabinoids

      • carbon monoxide, arthropod14 and snake venoms

      • Tricholoma equestre (mushroom)

      • antipsychotics, SSRIs, doxylamine

      • adalimumab, rituximab

    • extremes of temperature

    • inborn errors of metabolism

      • myophosphorylase deficiency

      • fatty acid oxidation disorders

    • limb ischemia

    • prolonged immobilization

  • traumatic

    • compartment syndrome

    • crush injury

    • electrocution

    • excessive muscle activity

      • generalized tonic-clonic seizures

      • long distance running

      • serotonin toxicity

      • neuroleptic malignant syndrome

      • metabolic myopathy (e.g. carnitine palmitoyltransferase II deficiency)

  • elevated serum creatinine kinase (CK)

    • at least five times upper limit of normal

  • hyperkalemia, hypophosphatemia, hypocalcemia

  • hyperuricemia, elevated lactate dehydrogenase

  • elevated aspartate aminotransferae

  • heme positive urine dipstick

    • with an absence of erythrocytes on microscopy

  • myoglobinuria, myoglobinemia

Rhabdomyolysis has a heterogeneously hypodense appearance on CT. There may be rim-enhancement on post-contrast images 7,8.

Edema throughout affected muscles with signal intensity reflecting the severity of an injury is seen in mild-moderate cases. When severe, features of myonecrosis will be demonstrated. Two types of MRI findings have been described 4,8:

  • type 1

    • T1: homogeneously iso to hyperintense

    • T2/STIR: homogeneously hyperintense

    • T1 C+ (Gd): homogeneously enhancing

  • type 2

    • T1: homogeneously/heterogeneously hyperintense

    • T2: heterogeneously hyperintense

    • T1 C+ (Gd): rim-enhancing

Described features include a loss of the organized fascicular sonographic architecture characteristic of muscle with hyperechoic and hyperechoic foci 9,10. The muscle may demonstrate an increase in thickness 11.

The release of intracellular contents (e.g. myoglobin) can result in the development of cardiac arrhythmias and acute kidney injury (~30%). Muscle edema may lead to compartment syndrome. Full recovery is possible with early treatment. 

For MRI appearances consider:

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