From the Guidelines
To evaluate Acute Kidney Injury (AKI), the primary laboratory tests include serum creatinine, blood urea nitrogen (BUN), and urine output measurement, which are essential for diagnosis, determining severity, and identifying the underlying cause. The diagnosis of AKI is based on an increase in creatinine by 0.3 mg/dL within 48 hours or an increase in serum creatinine to 1.5 times baseline within 7 days, or urine volume less than 0.5 mL/kg/hr for 6 hours 1.
Key Laboratory Tests for AKI Evaluation
- Serum creatinine: a cornerstone measurement for detecting and staging AKI
- Blood urea nitrogen (BUN): helps in assessing the severity of AKI
- Urine output measurement: crucial for diagnosing AKI, with output less than 0.5 mL/kg/hour for 6 hours suggesting kidney injury
- Urinalysis: to check for proteinuria, hematuria, and the presence of casts or crystals, aiding in determining the etiology
- Urine sodium and fractional excretion of sodium (FENa): help differentiate between prerenal causes (FENa <1%) and intrinsic renal damage (FENa >2%)
- Complete blood count: may reveal anemia or signs of hemolysis
- Electrolyte panels: to identify imbalances like hyperkalemia or metabolic acidosis that often accompany AKI Additional tests such as kidney ultrasound, complement levels, antinuclear antibodies, or ANCA testing may be necessary in specific cases to rule out obstruction or suspect glomerulonephritis 1.
Importance of Early Detection and Monitoring
Early detection and monitoring of AKI are critical, as AKI can lead to significant morbidity and mortality, and its incidence is rising worldwide 1. Monitoring patients with AKI involves measurements of serum creatinine and urine output to stage the severity of the condition 1. Patients at increased risk for AKI should be tested with measurements of serum creatinine and urine output to detect AKI, with the frequency and duration of monitoring individualized based on patient risk and clinical course 1.
From the Research
Labs Used to Evaluate Acute Kidney Injury (AKI)
The following labs are used to evaluate AKI:
- Serum creatinine level 2, 3, 4
- Complete blood count 2
- Urinalysis 2, 5, 4, 6
- Fractional excretion of sodium (FeNa) 2, 5
- Fractional excretion of urea (FeU) 5
- Ultrasonography of the kidneys 2, 3
- Serum and urinary biomarkers such as cystatin C, neutrophil gelatinase-associated lipocalin, and uric acid 4
- Urinary biochemistry, including measurement of sodium, chloride, phosphate, and strong ion difference (SIDu) 6
- Blood physicochemical parameters, including phosphate, unmeasured anions (SIG), and albumin 6
Additional Tests
Other tests that may be used to evaluate AKI include: