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.
On this page:
Clinical presentation
Symptoms and signs are varied, but a classic triad of muscle pain, weakness, and dark urine are described.
Pathology
Etiology
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
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
-
excessive muscle activity
generalized tonic-clonic seizures
long distance running
serotonin toxicity
neuroleptic malignant syndrome
metabolic myopathy (e.g. carnitine palmitoyltransferase II deficiency)
Markers
-
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
Radiographic features
CT
Rhabdomyolysis has a heterogeneously hypodense appearance on CT. There may be rim-enhancement on post-contrast images 7,8.
MRI
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
Ultrasound
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.
Treatment and prognosis
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.
Differential diagnosis
For MRI appearances consider: