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, drugs, 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 most people do not 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
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 within the muscles)
- Some drugs and toxic substances
- Infection (for example, influenza A or B virus, coxsackievirus, or the bacteria Staphylococcus aureus)
Some drugs and toxic substances (for example, statins) can cause direct muscle damage. Other drugs and toxic substances raise levels of drugs that could damage muscle (for example, drug interactions involving antibiotics). Still other drugs and toxic substances damage muscle indirectly by restricting blood supply to those muscles. For example, people who are sedated and immobile after taking drugs such as antianxiety agents, antipsychotics, cocaine, 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)
The three classic symptoms of rhabdomyolysis are muscle pain, weakness, and reddish-brown urine (caused by the high levels of the red-pigmented protein myoglobin that is dumped into the blood). However, this trio of symptoms is present in less than 10% of all people with rhabdomyolysis.
The symptoms of rhabdomyolysis vary, and about 50% of people have no muscle complaints at all. When present, muscle pain tends to affect the shoulders, thighs, lower back, and calves.
At a high concentration, myoglobin excreted into the urine (myoglobinuria) changes the color of the urine to red or brown and can be confirmed with a urine test. However, a person can have rhabdomyolysis without also having discolored urine.
Other signs and symptoms depend on the cause of the original muscle injury as well as on the complications of that injury (for example, fever in people with infection or changes in alertness in intoxicated people).
Acute kidney injury is very common, occurring in 15 to 50% of people who have rhabdomyolysis complications. Occasionally, rhabdomyolysis is complicated by disseminated intravascular coagulation (DIC), the presence of small blood clots in blood vessels throughout the body.
- A doctor’s evaluation
- Blood and urine tests
Doctors suspect rhabdomyolysis based on symptoms. The diagnosis is confirmed by blood tests.
Sometimes additional laboratory testing to detect myoglobin in the urine is done to confirm the diagnosis.
- Treatment of underlying cause
- Treatment of complications
In general, treatment is aimed at the cause and any complications of rhabdomyolysis.
Such treatment typically includes intravenous fluids to prevent and treat acute kidney injury.
If compartment syndrome is the cause of the rhabdomyolysis, a surgical procedure called a fasciotomy is done to relieve pressure inside the muscle. Relieving this pressure helps to reestablish healthy circulation in the affected tissue. Infections are treated with the appropriate drugs. Any drugs suspected of causing the rhabdomyolysis (for example, statins) are stopped. Electrolyte disturbances are corrected.