Rhabdomyolysis is the breakdown of skeletal muscle tissue, resulting in the release of muscle cell contents, including myoglobin, into the bloodstream. Myoglobinuria refers to the presence of myoglobin in urine, which can cause dark-colored urine and is often linked to rhabdomyolysis. This condition can have a wide range of causes and potentially fatal complications if not addressed promptly.
Potential Complications
- Acute Renal Failure: Myoglobin can obstruct renal tubules, leading to kidney damage.
- Cardiac Arrhythmias: Hyperkalemia (elevated potassium) from muscle breakdown affects heart rhythm.
- Respiratory Insufficiency: Weakness or failure of respiratory muscles.
- Bulbar Muscle Dysfunction: Affecting speech and swallowing.
- Encephalopathy: Due to metabolic disturbances.
Clinical Presentation
- Symptoms: Dark urine (pigmenturia), muscle pain, and swelling.
- Urine Test: Positive dipstick for blood but without red blood cells, indicating myoglobin.
- Creatine Kinase (CK): Levels >100× the upper limit of normal are diagnostic clues.
Causes
- Exogenous Causes:
- Trauma or direct injury.
- Animal toxins (e.g., snake bites).
- Drugs (including illicit substances and medications linked to neuroleptic malignant syndrome).
- Endogenous Causes:
- Exertion-Triggered Myoglobinuria: Often linked to metabolic disorders (e.g., glycogen storage diseases, lipid storage disorders, mitochondrial myopathies).
- Toxic Myoglobinuria: Associated with fever or infections, particularly in younger children, and often idiopathic.
Investigations
- Urinalysis: To confirm the presence of myoglobin.
- Serum Creatine Kinase: A key marker of muscle damage.
- Muscle Biopsy: After recovery, for underlying conditions like:
- Lipid Storage Myopathies
- Glycogen Storage Disorders
- Mitochondrial Myopathies
Key Management Principles
- Immediate Intervention: Early recognition is critical to prevent complications.
- Hydration and Monitoring: To protect kidney function and address electrolyte imbalances.
- Targeted Treatment: Based on underlying causes (e.g., infection control, stopping causative drugs).