Rhabdomyolysis Associated Acute Kidney Injury: What a Medical Student Should Know

It’s the first day of your nephrology rotation and you’re excited to get started. The first patient of the day is someone with a creatinine of 5 and your team thinks it’s possibly a case of rhabdomyolysis. Now, you need to see the patient and UpToDate has a lot of information on this topic. Unfortunately, some of the information is complicated and not at your level. Here is a nice paper you might like.

Bosch et al NEJM 2009

• Does this scenario sound familiar?

Here, we briefly described rhabdomyolysis and acute kidney injury. We tried to include all you need to know about this topic for your nephrology rotation.

Rhabdomyolysis is when an injury to skeletal muscle leads to myocyte necrosis and release of its intracellular contents into the blood stream. Intracellular contents include electrolytes, myoglobin, and other sarcoplasmic proteins (e.g. creatine kinase and lactate dehydrogenase).

The classic presenting triad of rhabdomyolysis is

1. muscle pain
2. weakness
3. dark urine.

 Speaking of dark urine, what does all of this have to do with the kidney? Rhabdomyolysis can cause acute kidney injury (AKI) due to several factors including myoglobin casts obstructing the renal tubules and interstitial edema from the injury causing low intravascular volume which leads to renal vasoconstriction. Common renal manifestations of acute rhabdomyolysis are granular casts, dark red or tea-colored urine, and a rise in serum creatinine. Although the urine looks like it contains blood, the red color comes from the myoglobin released from the muscle cells, not RBCs.

Distinguishing rhabdomyolysis from other conditions can be done with a few simple labs. Most notably, serum creatinine kinase will be elevated. Creatinine kinase is the enzyme in skeletal muscle cells that help them contract and is a marker for muscle damage. As with any condition that leads to significant cell necrosis, you will notice hyperkalemia, hyperuricemia, hyperphosphatemia, and hypocalcemia. If rhabdomyolysis is significant enough to cause kidney injury, the creatinine will be increased as well.

When you suspect that a patient has rhabdomyolysis, do not forget to order an ECG to screen for any arrhythmia due to electrolyte abnormalities. Afterwards, start IV fluids. In severe cases, the acute kidney injury may lead to kidney failure and patients may need some sort of renal replacement therapy.

On tests, look for a patient who has recently had some sort of crushing trauma or just finished extreme exercise who presents with dark red or tea-colored urine but with no red blood cells under the microscope. This patient might be a someone who was in a motor vehicle accident or who just finished a marathon.  However, anything that causes muscle tissue damage can lead to rhabdomyolysis including cocaine and alcohol use, vascular occlusion, and infection. It is also important to remember that rhabdomyolysis and muscle pain is a commonly tested side effect of statin.

Now, you are ready to see your patient. Good luck!

Post from Jennifer Kaplan, Baylor and video from Sayna Nourozi, MD, Fellow (Baylor)

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