From the Guidelines
Rhabdomyolysis is diagnosed through a combination of clinical assessment, laboratory tests, and patient history, with the most important diagnostic marker being an elevated serum creatine kinase (CK) level, typically at least 5 times the upper limit of normal (>1,000 U/L) 1. The diagnosis of rhabdomyolysis involves a thorough evaluation of the patient's symptoms, medical history, and laboratory test results.
Key Diagnostic Markers
- Elevated serum creatine kinase (CK) level, typically at least 5 times the upper limit of normal (>1,000 U/L) 1
- Elevated myoglobin in blood and urine, which can cause tea or cola-colored urine
- Hyperkalemia, elevated liver enzymes, metabolic acidosis, and elevated blood urea nitrogen and creatinine if kidney injury has occurred
- Urinalysis typically shows positive results for blood on dipstick testing but few or no red blood cells under microscopy due to myoglobinuria rather than hematuria
Additional Tests and Assessments
- Electrocardiogram, renal function tests, and electrolyte panels to assess complications
- Repeated bio-assessment combining plasma myoglobin, plasma creatine phosphokinase (CPK), and kalaemia measurements 1
- Bladder catheterization to monitor hourly urine output and urine pH, which should be maintained at 6.5 1
Importance of Early Diagnosis
Early diagnosis is crucial as prompt treatment with aggressive intravenous fluid administration can prevent acute kidney injury, the most serious complication of rhabdomyolysis.
Clinical Considerations
Clinicians should obtain a thorough history focusing on potential causes such as trauma, excessive exercise, medications (particularly statins), illicit drugs, infections, or metabolic disorders. Physical examination may reveal muscle tenderness, weakness, or swelling. Prompt recognition and treatment of rhabdomyolysis can significantly improve patient outcomes and reduce the risk of morbidity and mortality 1.
From the Research
Diagnosis of Rhabdomyolysis
Rhabdomyolysis is a potentially life-threatening clinical syndrome characterized by the breakdown of skeletal muscle cells and release of creatine kinase (CK), lactate dehydrogenase (LDH), and myoglobin into the plasma and interstitial space 2. The diagnosis of rhabdomyolysis can be challenging due to its nonspecific symptoms, and a high level of suspicion is required in the mind of the treating physician.
Diagnostic Markers
- Elevated creatine kinase (CK) levels are an important diagnostic marker of rhabdomyolysis, with a level at least 10 times the upper limit of normal typically considered diagnostic 3.
- Myoglobinuria is also a diagnostic marker of rhabdomyolysis 3.
- However, CK alone may not be a sensitive marker for rhabdomyolysis-induced acute kidney injury (AKI) in some cases, as seen in a case report where a patient presented with severe AKI and normal CK levels 4.
Clinical Presentation
- The clinical presentation of rhabdomyolysis encompasses a spectrum of patients ranging from those with asymptomatic increases in CK levels to those with fulminant disease complicated by AKI, severe electrolyte abnormalities, compartment syndrome, and disseminated intravascular coagulation 3.
- Patients may present with symptoms such as myalgias, muscle weakness, and dark urine 5.
Prognostic Markers
- Creatine kinase has been used as a biological marker for the identification of patients at high risk of AKI following rhabdomyolysis, with a peak creatine kinase of at least 5000 U/L being 55% specific and 83% sensitive for the prediction of AKI requiring renal replacement therapy (RRT) 6.
- The McMahon Score has also been validated as a prognostic marker, with a score of at least 6 calculated on admission being 68% specific and 86% sensitive for RRT 6.