Rhabdomyolysis and Acute Kidney Injury

Rhabdomyolysis is the breakdown of skeletal muscle that releases intracellular contents — including myoglobin, creatine kinase, potassium, and phosphate — into the circulation. When severe, the released myoglobin can injure the kidneys and cause a form of pigment-associated acute kidney injury, one of the classic intrinsic causes of AKI.

Definition

Rhabdomyolysis-associated acute kidney injury is AKI arising from the release of myoglobin and other muscle-cell contents into the circulation following skeletal-muscle breakdown, with myoglobin contributing to tubular injury, obstruction, and vasoconstriction.

Scope

The entry describes the causes of muscle breakdown, the mechanisms by which myoglobin contributes to kidney injury, and the associated metabolic disturbances, treating rhabdomyolysis-associated AKI as a reference syndrome within critical care nephrology. It does not provide individualized management advice.

Core questions

• What causes skeletal-muscle breakdown in rhabdomyolysis?
• By what mechanisms does myoglobin contribute to acute kidney injury?
• What metabolic disturbances accompany severe rhabdomyolysis?
• Why is it considered a pigment nephropathy?

Key concepts

• Skeletal-muscle breakdown
• Myoglobin release
• Creatine kinase elevation
• Pigment (myoglobinuric) nephropathy
• Tubular obstruction by casts
• Renal vasoconstriction
• Hyperkalemia and hyperphosphatemia
• Crush syndrome

Mechanisms

Muscle injury — from crush trauma, prolonged immobilization, ischemia, exertion, toxins, infections, or metabolic and inherited myopathies — disrupts the myocyte membrane and releases myoglobin and electrolytes. As described by Bosch and colleagues, filtered myoglobin contributes to AKI through three interacting mechanisms: renal vasoconstriction and medullary ischemia, direct tubular cytotoxicity (partly via iron-mediated oxidative injury), and intratubular cast formation that obstructs flow, the latter favored by acidic urine and volume depletion. Concurrent release of potassium and phosphate and sequestration of calcium produce characteristic metabolic disturbances.

Clinical relevance

Rhabdomyolysis is a recognized cause of intrinsic AKI, especially after trauma, crush injury, and severe exertion or immobilization, and understanding its mechanism explains the associated electrolyte disturbances and the role of myoglobin. This entry is descriptive and is not a basis for individual diagnosis or treatment.

Epidemiology

Rhabdomyolysis has many causes, and a variable proportion of cases — increasing with the severity of muscle injury and the height of creatine kinase and myoglobin levels, and with volume depletion or acidosis — progress to AKI; crush injury in disasters is a classic setting for severe, AKI-prone rhabdomyolysis.

Evidence & guidelines

The 2012 KDIGO guideline situates pigment nephropathy within AKI prevention and supportive care. The review by Bosch and colleagues is a widely cited synthesis of the pathophysiology and clinical features, and Ronco and colleagues place it among intrinsic causes of AKI.

History

The link between crushed muscle and acute renal failure was brought to prominence by observations of crush injuries during twentieth-century wartime and disaster medicine, which established 'crush syndrome' and identified myoglobin as the nephrotoxic pigment. Later work clarified the vasoconstrictive, cytotoxic, and obstructive components of the kidney injury.

Key figures

• Xavier Bosch
• Esteban Poch
• Josep M. Grau

Seminal works

• bosch-2009

Frequently asked questions

How does rhabdomyolysis injure the kidney?

Myoglobin released from damaged muscle contributes to kidney injury through renal vasoconstriction, direct tubular toxicity (in part via iron-mediated oxidative stress), and obstruction of the tubules by pigment casts, especially when urine is acidic and the patient is volume-depleted.

What laboratory finding signals significant muscle breakdown?

A markedly elevated serum creatine kinase, along with myoglobin in blood and urine, signals significant skeletal-muscle breakdown; severe elevations are associated with greater risk of kidney injury.