Which of these is a renal or intrarenal cause of acute renal failure?

• A. Injury from trauma
• B. Nephrotoxic drugs
• C. Nephron injury from trauma, nephrotoxic drugs, or infection
• D. Renal stones

Answer: (C)

Intrinsic (intrarenal) acute renal failure comes from damage inside the kidney itself, affecting the tubules, interstitium, or glomeruli. Nephron injury within the kidney can be caused by toxins (nephrotoxic drugs searing the tubular cells), direct trauma to the kidney, or infection that injures the renal parenchyma. Because it encompasses these internal injuries, selecting the option that lists nephron injury from trauma, nephrotoxic drugs, or infection best reflects intrarenal causes.

The other scenarios describe processes that typically cause problems outside the kidney itself or block urine flow after it leaves the kidney: trauma can lead to hypoperfusion or direct renal injury, but not necessarily an intrinsic renal insult; stones cause post-renal obstruction; and nephrotoxic drugs are only one of several intrarenal mechanisms, not the full scope.