Rhabdomyolysis

Mr Andrew Murphy and Dr Henry Knipe et al.

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 tried of muscle pain, weakness, and dark urine are described. 

Aetiology

Most common causes reported in Western adult populations is trauma/crush injury, exercise, cocaine and immobilisation. The range of causes is wide: 

  • non-traumatic
    • infection, e.g. infectious myositis
    • electrolyte abnormalities, e.g. hypokalemia, hypocalcaemia
    • immune-mediate, e.g. dermatomyositis, polymyositis
    • drugs, e.g. alcohol, cocaine, statins, anaesthetic agents, heparin
    • hyperthermia/hypothermia
    • metabolic disease, e.g. myophosphorylase deficiency
    • ischaemia
    • immobilisation
  • traumatic
Markers
  • serum creatinine kinase (CK) will be markedly raised (at least five times normal)
  • elevated serum potassium
  • positive urine myoglobin
CT

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

MRI

Oedema 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:

  • 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

The release of intracellular contents (e.g. myoglobin) can result in the development of cardiac arrhythmias, acute renal failure (~30%) and tetanus. Muscle oedema may lead to compartment syndrome. Full recovery with early treatment. 

For MRI appearances consider:

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Article Information

rID: 32722
Section: Pathology
Tag: cases
Synonyms or Alternate Spellings:

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