Figure 127

Acute renal failure (ARF). This figure depicts the most commonly used schema to classify and diagnostically approach the patient with ARF [1, 6, 9]. The most common general cause of ARF (60% to 70% of cases) is prerenal factors. Prerenal causes include those secondary to renal hypoperfusion, which occurs in the setting of extracellular fluid loss (eg, with vomiting, nasogastric suctioning, gastrointestinal hemorrhage, diarrhea, burns, heat stroke, diuretics, glucosuria), sequestration of extracellular fluid (eg, with pancreatitis, abdominal surgery, muscle crush injury, early sepsis), or impaired cardiac output. In most prerenal forms of ARF, one or more of the vasomotor mechanisms noted in Figure 12-8 is operative. The diagnostic criteria for prerenal ARF are delineated in Figure 12-9. Once prerenal forms of ARF have been ruled out, postrenal forms (ie, obstruction to urine flow) should be considered. Obstruction to urine flow is a less common (5% to 15% of cases) cause of ARF but is nearly always amenable to therapy. The site of obstruction can be intrarenal (eg, crystals or proteins obstructing the terminal collecting tubules) or extrarenal (eg, blockade of the renal pelvis, ureters, bladder, or urethra). The diagnosis of postrenal forms of ARF is supported by data outlined in Figure 12-10. After pre-and postrenal forms of ARF have been considered, attention should focus on the kidney. When considering renal forms of ARF, it is helpful to think in terms of renal anatomic compartments (vasculature, glomeruli, interstitium, and tubules). Acute disorders involving any of these compartments can lead to ARF.

Decreased Renal Perfusion Pressure

Afferent Arteriolar Constriction

Efferent Arteriolar Dilation

Extracellular fluid volume loss


Converting enzyme inhibitors

or sequestration

Medications (NSAIDs, cyclosporine,

Angiotensin II receptor antagonists

Impaired cardiac output

contrast medium, amphotericin,

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