What is the most common cause of acute renal failure?

• A. Acute tubular necrosis
• B. Acute glomerulonephritis
• C. Pyelonephritis
• D. Nephrolithiasis

Answer: (A)

Acute kidney injury most often arises from intrinsic renal damage, and within that category the most frequent cause is acute tubular necrosis. This condition occurs when tubular epithelial cells are injured, usually from ischemia due to hypotension or sepsis, or from exposure to nephrotoxins such as certain antibiotics, radiographic contrast, or toxins from rhabdomyolysis. When the tubules are damaged, they can’t reabsorb properly, and tubular obstruction plus back-leak into the bloodstream reduces the glomerular filtration rate, leading to oliguria and rising creatinine. The other options describe different renal processes or complications (infection of the kidney tissue, infection of the renal pelvis, or stone passage causing obstruction) that are less commonly the primary cause of acute renal failure compared with ATN.