• Syndrome characterized by muscle necrosis and the release of intracellular muscle constituents into the circulation.
• Complications can range from subclinical to acutely life threatening.
• Represents approximately 7 to 10% of all cases of acute kidney injury (AKI).
• AKI is independently associated with mortality in patients with rhabdomyolysis.
• The causes of rhabdomyolysis are numerous and therefore should be ruled out in any patient presenting with a traumatic or non-traumatic mechanism for muscle injury.
• Look for underlying causes: MI, shock, dead gut, dead limbs, occult seizures can all cause elevated CK.

Complications

• Acute renal failure (may be up to 33% of patients presenting with rhabdomyolysis).
• Hypovolemia from “third-spacing”.
• Hyperkalemia, hyperphosphatemia, hypocalcemia and hyperuricemia.
• Metabolic acidosis.
• Compartment syndrome.
• Disseminated intravascular coagulation.

Diagnosis

• Elevated serum CK levels.
• May have signs, symptoms, or a mechanism consistent with muscle injury.
• Consistent signs and symptoms are non-specific and not always present. The diagnosis, therefore, requires a high level of suspicion from the treating physician in the setting of elevated CK levels.

Causes

• Trauma (crush injuries, burns, electrocution).
• Exertion (strenuous exercise, seizures, alcohol withdrawal).
• Muscle hypoxia (limb compression, compartment syndrome, prolonged immobilization – coma or extended time on the ground).
• Genetic defects (disorders of glycolysis, glycogenolysis, lipid metabolism)
• Infections: viral (severe influenza), clostridium.
• Body temperature changes (hyperthermia, heat stroke, hypothermia)
• Metabolic and electrolyte disorders: thyroid storm, phaeochromocytoma, DKA, hypokalemia, hypophosphatemia
• Drugs and toxins:
  • Lipid lowering drugs,
  • Sedatives: heroin, alcohol (causing coma).
  • Stimulants: cocaine, amphetamines, malignant hyperthermia, serotonin syndrome, neuroleptic malignant syndrome.

Presentation

• Classic triad: myalgia, weakness and dark tea coloured urine (myoglobinuria).
• Muscle pain, when present is typically most prominent in proximal muscle groups (affected limb).
• Depending on the underlying etiology, patients may also present with malaise, nausea, vomiting and abdominal pain.

Physical

• Muscle tenderness.
• Muscle swelling.
• Muscle weakness.
• Depending on the underlying etiology, may see skin changes of ischemic tissue such as discoloration or blisters.
• If severe, shock due to third spacing, acidosis.

Investigations

• Serum CK > 5 times upper limit of normal at presentation:
  • No cut-off value that conclusively diagnoses rhabdomyolysis.
  • CK > 5,000 significant (some report to be 50%) risk of AKI.
  • Begins to rise 2 – 12 hours following muscle injury, reaches maximum within 24 hours.
• Blood urea nitrogen, creatinine, and routine electrolytes:
  • This is the focus rather than the CK level.
  • Acute kidney injury and severe electrolyte abnormalities are common.
• Urinalysis:
  • Myoglobinuria will have positive blood test on urine dipstick.
  • Red/brown urine; POS dipstick result for blood, few RBC on R&M highly suggestive but, if indicated, may require further lab tests), proteinuria.
  • Lab will evaluate the colour of the supernatant after centrifugation of the urine; hematuria will have a clear supernatant, whereas hemoglobinuria and myoglobinuria will not. To differentiate hemoglobinuria from myoglobinuria, evaluate the plasma colour; hemoglobinuria will have a pink to red plasma colour, whereas myoglobinuria will not.
• Complete blood count, including differential and platelet count.
• Calcium (can be low or high), phosphate, albumin, and uric acid (high):
  • Often abnormal.
• Venous blood gas (metabolic acidosis).
• Electrocardiography (hypocalcemia, hyperkalemia).
• Other investigations should be guided by your decision for the underlying etiology.

1. Bosch X, Poch E, Grau JM. Rhabdomyolysis and acute kidney injury. N Engl J Med. 2009;361(1):62–72.

   
   

2. Khan FY. Rhabdomyolysis: a review of the literature. Neth J Med 2009; 67:272.

   
   

3. Miller, Marc. Clinical manifestations and diagnosis of rhabdomyolysis .In: UpToDate, Post TW (Ed), UpToDate, Waltham, MA. (Accessed on November 21, 2020.)

   
   

4. Walls, Ron. Rosen’s Guide To Emergency Medicine 9th edition. Philadelphia, Elsevier INC, 2018.