Overview of Rhabdomyolysis

Rhabdomyolysis, sometimes called "rhabdo" in clinical parlance, implies "breakdown of muscles".  It is a clinical syndrome where muscles begin to breakdown and lead to alterations in the level of fluid and electrolytes in the body, thus leading to harmful consequences. 

Multiple factors have been associated with a rhabdomyolysis. Here are a few examples:

• Medications; eg. statins and fibrates (drugs used to lower cholesterol), colchicine (a gout medication), antibiotics, steroids, etc
• Excessive strenuous exercise which leads to a phenomenon called exercise-induced rhabdomyolysis or exertional rhabdomyolysis
• High temperatures causing heat stroke are a predisposing factor.
• Illicit drugs like cocaine and amphetamines

Typically, the affected patient will report extreme muscle pain, muscle stiffness, swelling, weakness, and sometimes "dark/cola-colored urine".  Dehydration is common, and the patient could have changes in mental status and low blood pressure leading to light-headedness, dizziness, decreased urine output, etc. Fever can be present as well. 

Rhabdomyolysis impacts the kidney function in multiple ways.  The breakdown of muscles leads to movement of body fluid out of the blood vessels into the injured muscle, essentially creating and worsening a state of dehydration.  This by itself is sometimes enough to cause a severe decline in kidney function, often called acute kidney injury.  Electrolyte levels can also change in the blood and can be manifested by:

• Increased phosphorus levels
• Decreased calcium levels
• Increased potassium levels
• Increased uric acid levels

Another way by which rhabdomyolysis hurts the kidney is a phenomenon called myoglobinuria. Myoglobin is a protein found in the muscles.  When muscles break down, this myoglobin is released into the blood from where it makes its way to the kidney. The kidneys are not good at excreting myoglobin and this protein besides being toxic to the kidneys' cells, will often clog up the kidneys' "drainage system" called the tubules. This could lead to kidney failure. In worst case situations, rhabdomyolysis-induced kidney failure because of myoglobinuria can lead to irreversible kidney failure requiring long-term dialysis.

The diagnosis of rhabdomyolysis depends on the clinical presentation which includes the symptoms and the signs of presentation like muscle aches.  Some more specific symptoms would include cola-colored urine.  Lab tests are done to support the diagnosis and will often show a significantly elevated level of a chemical in the blood called CPK or creatinine phosphokinase.  Kidney failure may be apparent on the ​blood test as well, with elevated creatinine levels.  A urine test might show the presence of myoglobin, the abnormal protein released into the urine from muscle breakdown.

Besides treating the primary cause that led to it, the crux of treatment of rhabdomyolysis is correcting the abnormal electrolyte levels and aggressive hydration of the affected patient with intravenous fluids.  There has been some debate about what kind of intravenous fluid is best for a patient in this situation.  In the past, alkalinizing the urine with sodium bicarbonate use to be the standard of care.  However, its superiority over other intravenous fluids like normal saline has never been emphatically proven.

The treating doctor will trend your kidney function while you are on the intravenous fluids. Typically, your symptoms and the kidney function should begin to recover over a couple of days, and the urine should begin to clear up. In some patients, however, the kidneys can develop injury to the point where dialysis might become necessary. Remember, dialysis is a supportive therapy. It does not treat the kidney failure per se; it only replaces the kidney function. If the kidneys are going to recover, they will do so on their own, and all that the patient and physician can do is to give them a supportive environment. Rarely, the patient could become dialysis-dependent for life.