From the Guidelines
Acute Kidney Injury (AKI) is characterized by an increase in serum creatinine of ≥0.3 mg/dL within 48 hours or an increase in serum creatinine to 1.5 times baseline within 7 days, or urine volume < 0.5 mL/kg/h for 6 hours, as defined by the KDIGO guidelines 1.
Definition and Diagnosis of AKI
AKI is a sudden decline in kidney function that develops over hours to days, resulting in the kidneys' inability to filter waste products from the blood effectively. The diagnosis of AKI is based on the KDIGO criteria, which include an increase in serum creatinine of ≥0.3 mg/dL within 48 hours or an increase in serum creatinine to 1.5 times baseline within 7 days, or urine volume < 0.5 mL/kg/h for 6 hours 1.
Laboratory Findings in AKI
On laboratory tests, AKI is characterized by elevated serum creatinine and often decreased urine output. Other laboratory findings may include elevated blood urea nitrogen (BUN), metabolic acidosis with decreased bicarbonate levels, hyperkalemia, hyperphosphatemia, and hypocalcemia. The BUN-to-creatinine ratio is typically elevated (>20:1) in prerenal AKI. Urinalysis may show proteinuria, hematuria, or the presence of casts depending on the underlying cause. The fractional excretion of sodium (FENa) is often low (<1%) in prerenal AKI but elevated (>2%) in intrinsic renal failure 1.
Clinical Significance of AKI
AKI has a significant impact on patient morbidity and mortality, with increased health care costs. The need for renal replacement therapy (dialysis or hemofiltration) indicates stage 3 AKI, the highest stage. AKI may be reversible or can lead to chronic kidney disease (CKD) 1.
Recent Guidelines and Recommendations
Recent guidelines and recommendations emphasize the importance of early detection and treatment of AKI, as well as the use of KDIGO criteria for diagnosis and staging 1. The AGA clinical practice update on the evaluation and management of AKI in patients with cirrhosis recommends the use of vasoconstrictor agents and albumin in certain cases, and emphasizes the importance of careful monitoring for fluid overload 1.
From the Research
Definition and Characterization of AKI
- Acute kidney injury (AKI) is defined as a sudden loss of excretory kidney function 2
- AKI is characterized by an abrupt decrease in renal function or the onset of frank renal failure 3
- It is also defined as an increase in serum creatinine or a decrease in urine output over hours to days 4
Laboratory Characteristics of AKI
- An increase in the serum creatinine (SCr) level of 0.3 mg/dL or more within 48 hours 3
- An SCr level increase of 1.5 times or more of the baseline level within 7 days 3
- A decrease in urine output to less than 0.5 mL/kg/hour for 6 hours 3
- Increase in serum creatinine level with or without reduced urine output 5
Diagnosis and Evaluation of AKI
- Diagnostic evaluation can be used to classify AKI as prerenal, intrinsic renal, or postrenal 5
- Initial workup includes a patient history to identify the use of nephrotoxic medications or systemic illnesses 5
- Physical examination should assess intravascular volume status and identify skin rashes indicative of systemic illness 5
- Initial laboratory evaluation should include measurement of serum creatinine level, complete blood count, urinalysis, and fractional excretion of sodium 5