Rhabdomyolysis is breakdown of muscle fibers. Muscle breakdown causes the release of myoglobin into the bloodstream. Myoglobin can cause kidney damage. Symptoms include dark urine, muscle weakness, and fatigue.
About 26,000 cases of rhabdomyolysis occur in the United States each year.
Rhabdomyolysis is always triggered by muscle injury. That injury can be caused by physical means (crushed by weight, starved by blocked blood vessel) or by chemical means (toxins, heat, or drugs).
The breakdown products when muscle is damaged include a protein called myoglobin. Myoglobin is related to hemoglobin. Both are proteins in the body. Hemoglobin transports oxygen in the blood; myoglobin stores oxygen in muscles. When myoglobin is released into the blood after muscle injury, it is filtered out of the body by the kidneys. Since myoglobin is toxic to the small tubules of the kidneys, high levels of this protein can damage the kidneys and may result in acute renal failure.
Many things can trigger rhabdomyolysis. Anything that damages the muscles can cause this condition.
Trauma, Heat, and Exertion
This includes a crush injury when something heavy falls on you. Overly intense exercise, heatstroke, or third-degree burns can trigger the syndrome.
Other causes in this category include:
- blocked blood vessels
- lightning strike
- intense shivering
- ischemic limb injury
- marathon running
- pathological muscle exertion
Genetic and Metabolic Disorders
Some people develop rhabdomyolysis because of genetic conditions such as problems with lipid (fat) metabolism, carbohydrate metabolism, or purine (a substance found in foods such as sardines, liver, asparagus) metabolism. Metabolic problems such as hypothyroidism (low thyroid hormone), diabetic ketoacidosis (build-up of ketones in the body), and electrolyte imbalances can also trigger rhabdomyolysis.
Other genetic disorders that can lead to rhabdomyolysis include:
- carnitine deficiency
- McArdle’s disease
- lactate dehydrogenase deficiency
- Duchenne’s muscular dystrophy
Infection and Inflammation
Many types of infection and inflammation (both chronic and acute) can cause rhabdomyolysis, including:
- viral infection
- bacterial infection
Medications and Toxins
One important cause of rhabdomyolysis that many people are exposed to is statin (cholesterol lowering) medications. Statins include atorvastatin (Lipitor), rosuvastatin (Crestor), pravastatin (Pravachol), etc. Although rhabdomyolysis only occurs in a few people who take statins, so many people take these medications that it is important to be aware of the risk.
The syndrome can also be caused by exposure to other drugs, certain toxins, and high levels of alcohol. Other drugs than can cause rhabdomyolysis include:
There are many other potential causes in these four categories beyond those listed.
The initial symptoms of rhabdomyolysis can be subtle. They are not specific and may mimic other conditions.
Your affected muscles will likely feel weak. You may have an intense ache at the site of the affected muscles. The muscle may be tender to the touch and swollen, and you may see bruising.
You will likely have dark, tea-colored urine. You may urinate less often. Fever is common, along with a general sense of malaise or “feeling sick.” You may experience vomiting and nausea as well as confusion and agitation. Sometimes you may notice weight gain. Some people feel joint pain. Seizures may occur in later stages of the condition.
One serious problem with muscle injury is “compartment syndrome.” Swelling inside of the muscle causes the tight bands that surround the muscle, called fascia, to block the blood flow into or out of a muscle. Blocking blood flow into a muscle can increase the amount of muscle damage.
Doctors will look and feel the larger muscles in your body, especially any that ache, to see if there is tenderness or if muscle tissue has died off.
Urine and blood tests will be done to confirm the diagnosis. The presence of myoglobin in the urine is an important indication of muscle breakdown and rhabdomyolysis.
Blood tests may be done to determine muscle health and kidney health, including:
- creatine kinase (CK): increased CK indicates muscle damage
- myoglobin levels in blood and urine
- calcium, which may leak from injured muscles
- CK isoenzymes—a form of creatine kinase
- creatinine (in blood and urine): high level indicates kidney damage
If a genetic disease is suspected as a cause for rhabdomyolysis, a test called a “forearm ischemic test” may be done. Blood is taken from a vein in the forearm, and then a tight blood pressure cuff is used to reduce the blood flow to the forearm. Then blood samples are taken again. Differences in the two samples may indicate a genetic problem that can make you very prone to developing rhabdomyolysis.
If discovered early in its progression, rhabdomyolysis can be successfully treated without long-term damage to the kidneys.
Getting enough fluid into the body is the first and most important treatment. Intravenous (IV) fluids—a saline solution given through a needle in your arm—must be started very quickly. This fluid should contain bicarbonate, which helps combat acid in the blood due to the muscle injury. Bicarbonate also helps flush the myoglobin out of the kidneys.
Medications such as bicarbonate and certain kinds of diuretics may be prescribed as well to help the kidneys keep functioning.
High potassium levels in the blood (hyperkalemia) and low blood calcium levels (hypocalcemia) may also be treated with appropriate IV fluids.
If kidney damage and acute renal failure have already started, you may need to receive dialysis. Dialysis is also called “extracorporeal blood purification.” Blood is taken out of the body and cleaned in a special machine in order to remove extra sodium, potassium, phosphates, and other waste products.
Long-term outlook depends on the extent of damage to your kidneys. If rhabdomyolysis is caught early, you may be able to avoid major complications and return to normal health in a few weeks. Even then, however, you may still have some lingering weakness and pain in your muscles.
If acute renal failure and kidney damage occur, there is a chance that your kidneys may be permanently damaged.
If you develop compartment syndrome, you may have permanent extensive muscle damage.
Several of the symptoms and complications of rhabdomyolysis are very serious and may result in death if left untreated.
One serious complication of rhabdomyolysis is kidney damage, such as acute tubular necrosis (damage to the tubular cells in the kidneys). This kind of damage leads to acute renal (kidney) failure. When the kidneys no longer function, toxins and waste products build up in the blood and can poison you.
Imbalances of electrolytes, such as potassium and calcium, can damage cells throughout the body, including the heart. Heart arrhythmias (irregular heartbeat) and even cardiac arrest can occur from these imbalances.
Hepatic inflammation (swelling in the liver) occurs in 25 percent of patients with rhabdomyolysis. This can lead to liver damage and additional problems with filtering toxins from the blood.
Disseminated intravascular coagulation is a possible complication of rhabdomyolysis. In this disorder, proteins that cause blood to clot become overactive. This causes tiny clots to form all over the body. Some of these clots can plug the vessels and cut off blood supply to various organs such as the liver, brain, or kidney.
Compartment syndrome occurs when swelling inside of injured muscles causes the muscle fascia (tight bands around the muscle) to tighten. This chokes off blood supply to those muscles and can permanently destroy muscle tissue.
Written by: Christine Case-Lo
Medically reviewed by George Krucik, MD