Acute kidney injury and indications for emergency dialysis

What it is

Acute kidney injury, formerly known as acute renal failure, is defined as an abrupt decline in renal function as measured by a rise in creatinine and BUN, or by oliguria or anuria.

Causes and risk

• Prerenal azotemia comes from decreased renal perfusion: true volume depletion, decreased EABV as in heart failure or cirrhosis, displacement of intravascular fluid as in sepsis or pancreatitis, renal artery stenosis, and afferent arteriole vasoconstriction as with NSAIDs. Sodium, water and urea are retained by the kidney in an attempt to conserve volume.
• Intrinsic renal failure is most commonly due to acute tubular necrosis from ischemia or toxins, and less commonly to acute glomerulonephritis such as RPGN or hemolytic uremic syndrome, or to acute interstitial nephritis. In ATN there is patchy necrosis, with debris obstructing the tubule and fluid backflow across the necrotic tubule, which reduces GFR.
• Postrenal azotemia is due to outflow obstruction from stones, BPH, neoplasia or congenital anomalies, and it develops only with bilateral obstruction or in a solitary kidney.
• Hepatorenal syndrome is acute kidney injury caused by liver disease, found by excluding other causes of acute kidney injury, including prerenal azotemia and tubular necrosis.