In rhabdomyolysis, which mechanism leads to AKI?

• A. Glomerular immune complex deposition
• B. Myoglobin-induced tubular injury
• C. Obstructive uropathy
• D. Tubular necrosis due to ischemia

Answer: (B)

In rhabdomyolysis, acute kidney injury mainly results from myoglobin causing tubular injury. When damaged muscle releases myoglobin, the kidneys filter it into the tubular lumen, where the heme moiety can release iron and generate reactive oxygen species, damaging tubular epithelial cells. In acidic urine, myoglobin can also precipitate and form pigmented casts that obstruct tubules, further impairing filtration. Ischemia from volume loss can worsen the injury, but the central driver is the direct toxic effect of myoglobin on the renal tubules (with possible obstruction from casts). Glomerular immune complex deposition is characteristic of certain glomerulonephritides, not rhabdomyolysis, and while tubular necrosis from ischemia can occur, it is not the primary mechanism in this context.