Acute renal failure (ARF) is abrupt deterioration of renal function sufficient to result in failure of urinary elimination of nitrogenous waste products (urea nitrogen and creatinine). This deterioration of renal function results in elevations of blood urea nitrogen and serum creatinine concentrations. While there is no disagreement about the general definition of ARF, there are substantial differences in diagnostic criteria various clinicians use to define ARF (eg, magnitude of rise of serum creatinine concentration). From a clinical perspective, for persons with normal renal function and serum creatinine concentration, glomerular filtration rate must be dramatically reduced to result in even modest increments (eg, 0.1 to 0.3 mg/dL) in serum creatinine concentration. Moreover, several studies demonstrate a direct relationship between the magnitude of serum creatinine increase and mortality from ARF. Thus, the clinician must carefully evaluate all cases of rising serum creatinine.
The process of urine formation begins with delivery of blood to the glomerulus, filtration of the blood at the glomerulus, further processing of the filtrate by the renal tubules, and elimination of the formed urine by the renal collecting system. A derangement of any of these processes can result in the clinical picture of rapidly deteriorating renal function and ARF. As the causes of ARF are multiple and since subsequent treatment of ARF depends on a clear delineation of the cause, prompt diagnostic evaluation of each case of ARF is necessary.
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