Beyond Empiricism: Diagnostic Value of Kidney Biopsy in Methicillin-Resistant Staphylococcus aureus Endocarditis-Associated Acute Kidney Injury.

As intravenous drug use increases, the incidence of right-sided infective endocarditis has also risen. Renal involvement is not uncommon in infective endocarditis, and treatment is often initiated empirically. However, in complex cases with multiple differential diagnoses, kidney biopsy remains the gold standard for establishing the underlying pathology. We report the case of a 35-year-old man with acute kidney injury in the setting of methicillin-resistant Staphylococcus aureus infective endocarditis related to intravenous drug use, untreated hepatitis C infection, and possible antibiotic-associated nephrotoxicity. To differentiate these potential causes, a renal biopsy was performed during active infection, providing direct histological evidence of immune complex-mediated glomerulonephritis.