AKI CALCULATOR
Guidelines
AKI Calculator is an automated version of the guidelines for staging AKI using RIFLE, AKIN, and KDIGO. These guidelines give two staging scores based on:
- Serum Creatinine (SCr)
- Urine Output (UO)
All three guidelines (RIFLE, AKIN, and KDIGO) have identical criteria for calculating UO based risk scores. However, each guideline differs slightly in the SCr based risk scores. These differences may be seen by toggling the displayed guideline on the website. For more details on the guidelines and equations, see the References.
AKI Calculator displays the maximum of the two stages between:
- Most recent UO based stage in an 8-hour window, and
- Most recent SCr based stage in a 24-hour window
AKI stage based on SCr is determined by evaluating SCr relative to a baseline SCr. If no baseline value is known, it is computed via the MDRD formula. AKI stage by SCr may use initiation of dialysis and evaluation of estimated glomerular filtration rate (eGFR) relative to baseline eGFR during calculation. The higher the SCr above the baseline (or lower eGFR below baseline), the higher the AKI stage.
AKI stage based on UO is determined by evaluating urine output normalized by body weight over time relative to a threshold/nominal value. Catheter insertion time is required to establish a starting time. UO entered in the input tab of the AKI Calculator must be at least 6 hours after the catheter insertion time to receive an AKI stage (score). The lower the UO below the threshold, the higher the AKI stage.
Assumptions For All Guidelines
- The baseline SCr is assumed to have occurred within 7 days.
- Upon catheter insertion, the bladder is completely emptied and urine output at that time does not contribute to staging.
- Urine output is evenly distributed over time since last measurement.
- After 24 hours from the most recent UO based score, the SCr based score will not be considered for the most recent maximum.
- After 8 hours from the most recent SCr based score, the UO based score will not be considered for the most recent maximum.
- Anuria is considered less than 50 mL of urine passed in 12 hours.
- No rules concerning patients under 18 years old were implemented.
Additional KDIGO Assumptions
- SCr values below the minimum threshold of the next stage and above the maximum threshold of the current stage, are assumed to be included in the current stage (e.g. 1.92 mg/dL is grouped with values from 1.5-1.9 mg/dL and not 2-2.9 mg/dL).
Additional AKIN and KDIGO Assumptions
- "Acute" is considered to be within an inclusive 48-hour window.
Additional RIFLE Assumptions
- "Acute" is considered to be within an inclusive 7 day window.
Additional MDRD Assumptions
- Baseline GFR is assumed to be 60 mL/min in the MDRD formula for calculating baseline SCr. Though, this can be changed by the user.