Acute renal failure
Acute renal failure
Acute renal failure is defined as an increased creatinine concentration in a short period of time or a sudden decrease of urine production (oliguria or anuria). Symptoms and signs of ARF depend on its cause and severity: hypertension, headache, change in weight, edema, oliguria, nocturia, fatigue, nausea, lethargy, confusion, seizures, delirium, and coma. Acute renal failure can have a prerenal, intrarenal or postrenal origin.
Prerenal ARF results from a decrease in renal blood flow, which can be caused by volume depletion due to trauma or burns, septic shock, and decreased cardiac output due to heart failure. The glomerular filtration rate (GFR) is reduced and the kidneys retain water and salt, causing oliguria, production of concentrated urine, and a progressive inability to excrete nitrogenous wastes.
(Intra)renal ARF can present at four different levels:
- A vascular cause can be due to thrombosis or embolic clots in the renal artery or to microangiopathy. This presentation can be seen in a patient with hypertensive crisis and hemolytic uremic syndrome (HUS).
- Glomerular disease (glomerulonephritis) is mostly of immunological origin, resulting in disrupted glomerular filtration. Progression of the inflammatory process leads to destruction of glomerulus and a decrease in the GFR.
- At the tubulointerstitial level, acute tubular necrosis (ATN) is the most prevailing problem. This necrosis can have many causes, including renal ischemia, nephrotoxic drugs (cisplatin, aminoglycosides, amphotericin B).
- Interstitial nephritis is a complex collection of disease processes with a poorly understood pathophysiology. An inflammatory process is initiated in the renal interstitium in response to a wide variety of stimuli (toxic, metabolic, infectious, immune, infiltrative), although allergic drug reactions are probably the most common causes.
- Postrenal ARF is due to a simple mechanical or functional obstruction to the free flow of urine precluding its excretion and producing renal failure.
What is true about acute renal failure?
Which of the following is NOT true regarding prognosis in acute renal failure?
