Acute renal failure

Acute renal failure (ARF) is a rapid loss of renal function due to damage to the kidneys, resulting in retention of nitrogenous (urea and creatinine) and non-nitrogenous waste products that are normally excreted by the kidney. Depending on the severity and duration of the renal dysfunction, this accumulation is accompanied by metabolic disturbances, such as metabolic acidosis (acidification of the blood) and hyperkalaemia (elevated potassium levels), changes in body fluid balance, and effects on many other organ systems. more...

It can be characterised by oliguria or anuria (decrease or cessation of urine production), although nonoliguric ARF may occur. It is a serious disease and treated as a medical emergency.

Causes

Renal failure, whether chronic or acute, is usually categorised according to pre-renal, renal and post-renal causes:

• Pre-renal (causes in the blood supply):
  • hypotension (decreased blood supply), usually from shock or dehydration and fluid loss, heart attack
  • vascular problems, such as atheroembolic disease and renal vein thrombosis (which in part may be secondary to loss of coagulation factors due to renal dysfunction)
• Renal (damage to the kidney itself):
  • infection
  • toxins or medication (e.g. some NSAIDs, aminoglycoside antibiotics, amphotericin B, iodinated contrast, lithium)
  • rhabdomyolysis (breakdown of muscle tissue) - the resultant release of myoglobin in the blood affects the kidney; it can be caused by injury (especially crush injury and extensive blunt trauma), statins, MDMA (ecstasy) and some other drugs
  • hemolysis (breakdown of red blood cells) - the hemoglobin damages the tubules; it may be caused by various conditions such as sickle-cell disease, and lupus erythematosus
  • multiple myeloma, either due to hypercalcemia or "cast nephropathy" (multiple myeloma can also cause chronic renal failure by a different mechanism)
  • Acute glomerulonephritis which may due to a variety of causes, such as anti glomerular basement membrane disease/Goodpasture's syndrome, Wegener's granulomatosis or acute lupus nephritis with systemic lupus erythematosus
• Post-renal (causes in the urinary tract):
  • urinary retention (as a side-effect of medication or due to benign prostatic hypertrophy, kidney stones)
  • pyelonephritis
  • obstruction due to abdominal malignancy (e.g. ovarian cancer, colorectal cancer)

Diagnosis

Renal failure is generally diagnosed either when creatinine or blood urea nitrogen tests are markedly elevated in an ill patient, especially when oliguria is present. Previous measurements of renal function may offer comparison, which is especially important if a patient is known to have chronic renal failure as well. If the cause is not apparent, a large amount of blood tests and examination of a urine specimen is typically performed to elucidate the cause of acute renal failure, medical ultrasonography of the renal tract is essential to rule out obstruction of the urinary tract.

Consensus criteria for the diagnosis of ARF are:

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