Acute tubular necrosis

What it is

Acute tubular necrosis is the most common cause of acute kidney injury in hospitalized patients, and it is the most common cause of intrinsic renal failure. There is patchy necrosis with debris obstructing the tubule and fluid backflow across the necrotic tubule, so GFR falls. Urea reabsorption is impaired, so the BUN to creatinine ratio falls.

The main tubule susceptible to injury is the PCT. ATN spontaneously resolves in many cases, but it can be fatal, especially during the initial oliguric phase. The key finding is granular, muddy brown casts.

Causes and risk

ATN is caused by ischemic or nephrotoxic injury.

Ischemic ATN follows a fall in renal blood flow, for example hypotension, shock, sepsis, hemorrhage or HF. It results in death of tubular cells that may slough into the tubular lumen. The PCT and thick ascending limb are highly susceptible to injury.

Nephrotoxic ATN follows injury from toxic substances:

• Aminoglycosides
• Radiocontrast agents
• Lead
• Cisplatin
• Ethylene glycol

Crush injury with myoglobinuria and hemoglobinuria also cause it, and here the proximal tubules are particularly susceptible. ATN is usually associated with hypotension, acute blood loss, sepsis or rhabdomyolysis.