Rhabdomyolysis

Rhabdomyolysis occurs when muscle fibers damaged by disease, injury, or toxic substances break down and release their contents into the bloodstream. Severe disease can cause acute kidney injury.

• Common causes include muscle injury and impaired blood flow in damaged tissue, medications, toxic substances, and infections.

• Less common causes include electrolyte imbalances, endocrine and genetic disorders, extreme exercise, and extremes in body temperature.

• Symptoms can include muscle pain, weakness, and reddish-brown (or tea-colored) urine, but few people have all of these symptoms.

• Serious complications include acute kidney injury (also called acute kidney failure).

• Diagnosis is with blood and urine tests. 

• Treatments are aimed at the cause and any resulting complications (for example, acute kidney injury is treated with intravenous fluids and sometimes dialysis).

(See also Overview of Kidney Failure.)

Normal skeletal muscle function requires proper exchange of electrolytes (electrically charged minerals such as sodium and potassium) across muscle cells (myocytes). This exchange allows the cells to adequately metabolize adenosine triphosphate (ATP), a molecule necessary for transporting energy within cells and powering the body’s functions. 

In rhabdomyolysis the processes that support the normal functioning of skeletal muscle are disrupted, so that myocytes break down and release some of their contents into the bloodstream, including

• Creatine kinase (CK), a protein that rises when muscle is damaged

• Myoglobin, an iron-containing protein that transports and stores oxygen in myocytes

• Electrolytes

When the kidneys are functioning normally, they filter all myoglobin and excess creatine kinase out of the bloodstream through urination. High concentrations of myoglobin in the blood can overwhelm and damage the kidneys (causing acute kidney injury) and other organs.

Any form of muscle damage can result in rhabdomyolysis. The most common causes of that damage include

• Direct injury of the muscle or impairment of blood flow in muscle tissue, such as occurs in crush injuries, electric shocks, seizures, or compartment syndrome (a painful condition characterized by dangerously high levels of pressure in the affected muscle)

• Some medications and toxic substances

• Infection (for example, influenza A or B virus, coxsackievirus, or the bacteria Staphylococcus aureus)

Some medications and toxic substances (for example, statins) can cause direct muscle damage. Other medications and toxic substances raise levels of medications that could damage muscle (for example, drug interactions involving antibiotics). Still other medications and toxic substances damage muscle indirectly by restricting blood supply to those muscles. For example, people who are sedated and immobile after taking medications such as antianxiety agents, antipsychotics, , amphetamines, or alcohol may stay in the same position for hours, which can lead to compression and damage of certain muscles and the blood vessels to those muscles.

Less common causes of rhabdomyolysis include

• Electrolyte disorders (for example, low blood levels of potassium [hypokalemia] or phosphate [hypophosphatemia])

• Endocrine disorders (for example, diabetic ketoacidosis)

• Genetic disorders (for example, Duchenne muscular dystrophy or Becker muscular dystrophy)

• Extreme exercise

• Prolonged bed rest

• Extremes in body temperature (for example, hypothermia [low body temperature]; and disorders accompanied by hyperthermia [high body temperatures], such as neuroleptic malignant syndrome, malignant hyperthermia, and heatstroke)