Presentation
50 year old male 2 days ago cycled 20 km followed by increasing thigh pain. Creatine kinase (CK) - 17994H (normal 30-200)
Patient Data
MRI left thigh:
Coronal and axial sequences have been obtained.
Extensive gross muscular edema and swelling is identified in the anterior compartment of the left thigh, involving almost the entirety of vastus medialis, and 70 - 80% of vastus lateralis and vastus intermedius. Rectus femoris is spared. A thin layer of fluid tracks along fascial planes between the anterior compartment musculature. No focal muscular or myotendinous junction tear. No signal abnormality identified in muscle bellies of the posterior or medial compartments of the left thigh. Incompletely imaged on the coronal sequence, there is evidence of less pronounced muscular edema in the contralateral right vastus medialis. No mass lesion. No bone marrow edema.
Conclusion: Appearance is consistent with exercise induced muscle edema/injury.
Case Discussion
History of pain post exercise and elevated CK leads to a diagnosis of rhabdomyolysis. One of the complications of this condition is compartment syndrome. The clinical finding of anterior compartment syndrome is presumably secondary to the muscular swelling. If the intramuscular signal change was secondary to compartment syndrome, none of the anterior compartment musculature would have been spared.
Rhabdomyolysis can be due to a number of conditions including: excessive exercise, crush injury, arterial occlusion, metabolic disturbance, drugs and toxins, infection, inflammation and congenital disorders. Excessive exercise and heat stroke are probably the most common cause of severe rhabdomyolysis.
MRI is usually not required for the diagnosis of rhabdomyolysis since it is a clinical diagnosis. It may be used for staging or follow-up or as in this case to confirm absence of another condition such as vascular malformation and hemorrhage that may have led to the muscle swelling.
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