Monday, December 6, 2010

Acute Renal Failure

Acute renal failure is a syndrome of varying causation that results in a sudden decline in renal function. It is frequently associated with an increase in BUN and creatinine, oliguria (less than 500 mL urine/24 hours), hyperkalemia, and sodium retention.

Pathophysiology of Acute renal failure
Three well-defined stages: oliguric or anuric, diuretic, and convalescent.
1. Oliguric

  • Filtration capability is reduced because of debris and damage to renal tubules.
  • Output is greatly reduced may be less than 400 mL/day.
  • If anuria present, catastrophic injury has likely occurred in both kidneys as in obstructive uropathy or, less commonly, in bilateral renal artery occlusion, acute cortical necrosis, or rapidly progressive glomerulonephritis (Agraharkar & Gupta, 2007).

2. Diuretic

  • May skip oliguric phase and begin to make large quantities (may be several liters) of urine
  • Client with oliguria will progress through diuretic phase during recovery.
  • Urine is dilute because of kidney’s inability to concentrate.

3. Convalescent

  • Renal blood flow and filtration improves.
  • Process of recovery is gradual, often weeks to months; in many cases, some degree of renal insufficiency persists.

Acute renal failure Classification
Classification dependent on site:

  1. Prerenal failure (azotemia): decreased renal perfusion manifested by reduced urine output because of decreased glomerular filtration rate (GFR)
  2. Renal or intrinsic failure: associated with parenchymal changes with damage to the renal tubules (acute tubular necrosis [ATN]) caused by ischemia or nephrotoxic substances
  3. Postrenal failure: results from an obstruction in the urinary tract anywhere from the tubules to the urethral meatus

Acute renal failure Clinical Manifestations

  1. Prerenal decreased tissue turgor, dryness of mucous membranes, weight loss, hypotension, oliguria or anuria, flat neck veins, tachycardia
  2. Postrenal obstruction to urine flow, obstructive symptoms of BPH, possible nephrolithiasis
  3. Intrarenal presentation based on cause; edema usually present
  4. Changes in urine volume and serum concentrations of BUN, creatinine, potassium, and so forth, as described above

Multiple causes: ischemia and toxicity (most common), obstructions

  • Prerenal failure: blood volume depletion due to hemorrhage, “third-space” sequestration of fluid as in edema or ascites in advanced liver disease, or burns; dehydration due to gastrointestinal (GI) losses or overuse of diuretics; septic or anaphylactic shock; heart failure (HF) with renal insufficiency, myocardial infarction (MI), trauma; renal artery obstruction; and use of certain drugs, such as nonsteroidal anti-inflammatory drugs (NSAIDs), cyclooxygenase inhibitors, angiotensin-converting enzyme (ACE) inhibitors
  • Intrinsic failure: ischemia and hypoperfusion similar to prerenal hypoperfusion (except that correction of the causative factor may be followed by continued oliguria for up to 30 days) associated with prolonged acute renal failure (ARF), blood transfusion reaction, or renal artery stenosis; and direct damage from nephrotoxic substances, such as radiocontrast media, cyclosporine, heavy metals (e.g., lead, mercury), cytotoxic drugs (e.g., certain chemotherapy agents), certain antibiotics (e.g., carbenicillins, aminoglycosides)
  • Postrenal failure: most commonly occurs with stones in the ureters, bladder, or urethra; from trauma or edema associated with infection, prostatic hypertrophy, or cancer; cervical cancer; strictures of renal artery
  • If underlying cause is corrected, the nephrons may recover; however, in some cases, damage is permanent and renal failure becomes chronic.

Community- or hospital-acquired

  • Most community-acquired ARF is secondary to volume depletion; as many as 90% of cases are estimated to have a potentially reversible cause.
  • Hospital-acquired ARF often occurs in the intensive care unit (ICU) setting and is commonly the end result of multiorgan failure.

Risk factors: advanced age, chronic infection, diabetes, hypertension, immune disorders such as lupus or scleroderma

COMPLICATIONS Acute Renal Failure

  • Infection
  • Arrhythmias due to hyperkalemia
  • Electrolyte (sodium, potassium, calcium, phosphorus) abnormalities
  • GI bleeding due to stress ulcers
  • Multiple organ systems failure


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