Lab abnormalities commonly seen in rhabdomyolysis
What laboratory abnormalities are commonly seen in patients with rhabdomyolysis?
Common laboratory findings in rhabdomyolysis include an increase in muscle enzyme levels (e.g., creatinine kinase), hyperkalemia, hypocalcemia, hyperphosphatemia, hyperuricemia, and an anion gap acidosis.
Potassium and phosphorus are released from damaged muscle cells into the circulation as muscle cells are lysed.
If muscle injury is coupled with Acute Kidney Injury, the excretion of potassium and phosphorus by the kidneys is further impaired.
By contrast, calcium levels in rhabdomyolysis are typically decreased as calcium precipitates in injured muscle and occasionally massive heterotropic calcification occurs.
High phosphorus levels contribute to hypocalcemia by directly binding free calcium and inhibiting 1aa-hydroxylase (the enzyme that catalyzes the conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol, the active form of vitamin D).
An anion gap metabolic acidosis is seen from the combination of anaerobic respiration in hypoxic muscles (lactic acidosis) and the accumulation of organic acids from Acute Kidney Injury.
Elevated uric acid levels are a direct result of the release of purine nucleosides from degrading muscle cells.
It should be noted that a low urine pH promotes the formation of tubular myoglobin casts and uric acid crystals, both of which can lead to tubular obstruction in the development of Acute Kidney Injury.