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 is trauma/crush injury, exercise, cocaine and immobilisation. The range of causes is wide:
- 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
- metabolic disease, e.g. myophosphorylase deficiency
- crush injury
- excessive muscle activity, e.g. overexercise, severe forms of delayed onset muscle soreness (DOMS)
- serum creatinine kinase (CK) will be markedly raised (at least five times normal)
- elevated serum potassium
- positive urine myoglobin
Rhabdomyolysis has a heterogeneously hypodense appearance on CT. There may be rim-enhancement on post-contrast images 7.
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:
- T1: homogeneously iso to hyperintense
- T2/STIR: homogeneously hyperintense
- T1 C+ (Gd): homogeneously enhancing
- T1: homogeneously/heterogeneously hyperintense
- T2: heterogeneously hyperintense
- T1 C+ (Gd): rim-enhancing
Treatment and prognosis
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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- 2. May DA, Disler DG, Jones EA et-al. Abnormal signal intensity in skeletal muscle at MR imaging: patterns, pearls, and pitfalls. Radiographics. 2000;20 Spec No (suppl_1): S295-315. doi:10.1148/radiographics.20.suppl_1.g00oc18s295 - Pubmed citation
- 3. Chakera A, Cowan N, Winearls C. Clinical Kidney Journal. 2008;1 (5): . doi:10.1093/ndtplus/sfn092
- 4. HAW-CHANG, YU-CHING CHENG HOWARD, and LAN CHUN-HSI SHIH. "Magnetic Resonance Imaging of Rhabdomyolysis: Muscle Necrosis Versus Ischemia."
- 5. Mirvis SE, Soto JA, Shanmuganathan K et-al. Problem Solving in Emergency Radiology: Expert Consult - Online. Saunders. ISBN:B00N04AZQC. Read it at Google Books - Find it at Amazon
- 6. Huerta-Alardín AL, Varon J, Marik PE. Bench-to-bedside review: Rhabdomyolysis - an overview for clinicians. Crit Care. 2006;9 (2): 158-69. doi:10.1186/cc2978 - Free text at pubmed - Pubmed citation
- 7. Lu CH, Tsang YM, Yu CW et-al. Rhabdomyolysis: magnetic resonance imaging and computed tomography findings. J Comput Assist Tomogr. 2007;31 (3): 368-74. doi:10.1097/01.rct.0000250115.10457.e9 - Pubmed citation