Kidney Disease: Acute Kidney Injury

Acute kidney injury (AKI) is characterized by an abrupt decrease in renal function or the onset of frank renal failure. Kidney Disease: Improving Global Outcomes (KDIGO) defines AKI as an increase in the serum creatinine (SCr) level of 0.3 mg/dL or more within 48 hours, an SCr level increase of 1.5 times or more of the baseline level within 7 days, or a decrease in urine output to less than 0.5 mL/kg/hour for 6 hours. AKI severity is determined by the degree of SCr increase or decrease in urine output. AKI typically is caused by systemic illness or toxic exposure. Thus, determining the cause is critical when possible. The history should focus on risk factors, including nephrotoxic drugs. The physical examination should include determination of fluid volume status. Urinalysis with microscopy can narrow the differential diagnosis. AKI management includes control of the underlying cause, achievement and maintenance of euvolemia, nutritional optimization, blood glucose control, and pharmacotherapy. Treatment with fluid resuscitation or diuresis is guided by the volume status. Emergent referral to a nephrology subspecialist is recommended for patients with stage 2 or 3 AKI; patients with stage 1 AKI and a concomitant, decompensated condition; or if the etiology of the AKI is unclear. Urgent referral should be considered if the injury does not improve with treatment or if glomerulonephritis is suspected.