Acute renal failure in the critically ill patient

Acute renal failure (ARF) is defined as a fall glomerular filtration rate (GFR) and the accumulation of nitrogenous wastes, including blood urea nitrogen (BUN) and creatinine. The term acute renal failure is used when the fall in GFR occurs relatively rapidly, and the BUN and creatinine levels increase over the course of days to weeks. In chronic renal failure, the GFR falls much more slowly, over months to years. Acute renal failure is seldom a community-acquired disease but usually develops in hospitalized patients. It complicates the course of approximately 5% of all hospitalized patients [3,28]. Critically ill patients have the highest incidence of ARF (>20%) [3,34]. The causes of ARF traditionally are divided into three categories: (1) prerenal ARF, (2) ARF caused by obstruction of the urinary-collecting system (postrenal ARF), and (3) ARF caused by acute instrinsic renal diseases. This longstanding, simple clinical classification of ARF remains useful, because it provides a logical basis for the diagnosis and treatment of ARE The most common causes of ARF are prerenal failure (similar to35% of cases) and acute tubular necrosis (ATN) (similar to50% of cases). Obstruction accounts for approximately 10% of cases, whereas intrinsic diseases of the kidney other than ATN account for the minority of cases [50]. This article is not intended to provide an exhaustive review of all aspects of ARE It focuses on prerenal failure and ATN, the most common causes of ART. Some of the intrinsic renal diseases other than ATN that can cause ARF are discussed in other articles in this issue. These diseases include vasculitis and glomerulonephritis (see article by Merkel et al.), the hepatorenal syndrome (see article by Briglia and Anania), and thrombotic microangiopathies (see article by Appel et al.). ARF caused by acute interstitial nephritis is discussed in many reviews [23,43].