Which condition may cause the intrinsic (intrarenal) form of acute renal failure?

• A. Nephrotoxic injury secondary to contrast media
• B. Obstructive uropathy
• C. Hemodynamic hypoperfusion
• D. Acute glomerulonephritis

Answer: (A)

Intrinsic (intrarenal) AKI happens when the damage is inside the kidney itself, such as injury to the tubular cells from toxins, inflammation of the interstitium, or glomerular disease. Nephrotoxic injury from contrast media is a classic intrarenal insult because the contrast directly damages the tubular epithelium, leading to acute tubular necrosis and a fall in GFR. This injury is within the kidney rather than due to reduced blood flow elsewhere or an obstruction in the urinary tract.

Obstructive uropathy causes a postrenal AKI from urine flow blockage, not intrarenal tissue injury. Hemodynamic hypoperfusion leads to prerenal AKI due to decreased renal perfusion and, if severe or prolonged, can progress to intrinsic damage but starts outside the kidney. Acute glomerulonephritis is an intrinsic kidney disease affecting the glomeruli and can cause AKI as well, but the scenario given is most directly illustrating nephrotoxic injury from contrast as a representative intrarenal cause.