Acute Renal Failure

Posted by e-Medical PPT
To function properly, the kidney requires: (1) normal blood flow; functioning glomeruli and tubules to separate and process an ultafiltrate containing waste products from the blood; and (3) drainage and elimination of formed urine from the body. The sudden interruption of any of these processes will lead to Acute Renal Failure (ARF). Disorders causing ARF are classified on the basis their primary site of interference with these processes. Conditions which interfere with blood delivery to the kidney are called Prerenal, and are most commonly functional (and potentially reversible) in nature (e.g., ECF volume contraction, congestive heart failure) but on occasion may be structural (e.g., renal artery stenosis). Diseases which cause intrinsic injury to the kidney proper (glomeruli, tubules, interstitium, small blood vessels) are grouped under Renal causes of ARF (e.g., acute glomerulonephritis, acute tubular necrosis, acute interstitial nephritis or small vessel vasculitis). Acute Tubular Necrosis is a distinctive clinicopathological syndrome in which the tubules are the primary site of injury. The terms ARF and ATN should not be used interchangeably. Finally, conditions which interfere with normal drainage and elimination of formed urine are classified as Postrenal (e.g., prostatic outlet obstruction, bilateral ureteral obstruction). Pre-renal ARF (also commonly referred to as “pre-renal azotemia”) and acute tubular necrosis (ATN) are the most common causes of acute renal failure in hospitalized patients.

Some combination of hypovolemia, hypotension and diminished renal perfusion is the most common cause of ARF in hospitalized patients. Identification of pre-renal (functional) ARF is important because it is generally reversible. Pre-renal ARF may evolve from blood loss, sodium depletion (due to diarrhea, excessive diuresis or congenital or acquired salt-wasting disorders), redistribution of plasma volume to a so-called “third space” (e.g., ascites in patients with hemorrhagic pancreatitis or hepatic cirrhosis), or reductions in effective arterial blood volume with consequent renal hypoperfusion (as in congestive heart failure, hepatic cirrhosis or nephrotic syndrome). In other situations, especially when for one reason or another renal perfusion is tenuous or already compromised, drugs which affect afferent and/or efferent arteriolar resistance (e.g., NSAIDs, ACE inhibitors) can precipitate pre-renal azotemia....

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