Signs and Symptoms of Rhabdomyolysis
Rhabdomyolysis classically presents with the triad of muscle pain, muscle weakness, and dark (red-to-brown) urine, though many patients present with incomplete or atypical symptoms.
Cardinal Clinical Features
The most consistent clinical manifestations include 1, 2:
- Muscle pain (myalgia) - typically diffuse, may involve proximal muscle groups preferentially
- Muscle weakness - generalized or localized
- Dark urine - red-to-brown coloration from myoglobinuria (though not always present or reported)
Common Presenting Complaints
In emergency settings, patients frequently present with 3:
- Generalized fatigue and weakness (47.1% of cases)
- Muscle pain (21.4%)
- Altered mental status (29.2% as symptom, 17.5% as chief complaint)
- Extremity pain (24.7%)
- Diffuse body aches (21.1%)
- Unresponsive state without clear etiology (20.8%)
- Nonsyncopal falls (17%)
Atypical Presentations
Be alert for atypical presentations, particularly in older adults or those with prolonged disease courses 4:
- Limb swelling and weakness without myalgia
- Absence of dark urine
- Modest CK elevations that persist for extended periods (1-3 months)
- Symptoms developing over hours to days after inciting event 2
Associated Physical Findings
In severe cases, particularly with malignant hyperthermia-related rhabdomyolysis 5:
- Exposed skin may be hot, flushed, and sweaty
- Skin mottling (more common in young children)
- Muscle swelling - may indicate compartment syndrome risk
- Tachycardia - from increased sympathetic activity
- Hyperthermia - progressive temperature elevation
Laboratory Confirmation
While not strictly "signs and symptoms," diagnosis requires 1, 2:
- Markedly elevated creatine kinase (CK) - typically >1,000 IU/L, often >50,000 IU/L in severe cases
- Elevated serum myoglobin
- Myoglobinuria on urinalysis
- Hyperkalemia - potentially severe enough to cause cardiac arrest 5
- Elevated creatinine - indicating potential acute kidney injury 6
Critical Pitfalls
Do not wait for the complete triad - many patients present with only one or two features. Muscle pain may be absent in sedated, altered, or elderly patients 6. The absence of dark urine does not exclude rhabdomyolysis, as myoglobinuria may be intermittent or diluted 4.
Symptoms typically manifest within 1 week of the inciting event 7, though the timeline varies. In trauma settings, monitor for evolving symptoms over the first 24 hours 6.