Enter Collection and Lab Data
This version estimates urine flow, urea clearance, creatinine clearance, mean residual renal function, body surface area, and normalized results.
Example Data Table
| Item | Example Value | Unit | Notes |
|---|---|---|---|
| Collection time | 24 | hours | Timed urine collection period. |
| Total urine volume | 900 | mL | Total measured urine collected. |
| Urine urea | 480 | mg/dL | Measured urine urea concentration. |
| Serum urea | 60 | mg/dL | Measured blood urea concentration. |
| Urine creatinine | 85 | mg/dL | Measured urine creatinine concentration. |
| Serum creatinine | 6.0 | mg/dL | Measured blood creatinine concentration. |
| Height / Weight | 170 / 70 | cm / kg | Used for body surface area. |
| Estimated mean residual renal function | 6.93 | mL/min | Average of urea and creatinine clearances. |
| Normalized mean residual renal function | 6.59 | mL/min/1.73 m² | Adjusted for body surface area. |
Formula Used
V = Total urine volume ÷ Collection time in minutes
Curea = (Urine urea × V) ÷ Serum urea
Ccr = (Urine creatinine × V) ÷ Serum creatinine
RRF = (Curea + Ccr) ÷ 2
BSA = 0.007184 × Height(cm)0.725 × Weight(kg)0.425
Normalized value = Measured value × (1.73 ÷ BSA)
These formulas assume properly timed urine collection and matched serum sampling. Unit conversions are applied internally before calculation.
How to Use This Calculator
Enter the urine collection duration and the total urine volume produced in that period. Add urine and serum urea concentrations, then urine and serum creatinine concentrations. Provide height and weight so the calculator can estimate body surface area and normalize the result.
Press the calculate button to display results above the form. The output includes urine flow, daily urine output, urea clearance, creatinine clearance, mean residual renal function, body surface area, and normalized clearances. Use the graph to compare absolute and normalized values quickly.
Use the CSV button to save the result table in spreadsheet-friendly form. Use the PDF button to generate a printable report. For repeated monitoring, keep the same collection method and unit conventions each time.
Frequently Asked Questions
1) What does residual renal function mean?
It describes the kidney clearance that still remains despite advanced kidney disease or dialysis. Tracking it can help show how much native filtration is still contributing between treatments.
2) Why average urea and creatinine clearance?
Urea can underestimate filtration because of reabsorption, while creatinine can overestimate it because of tubular secretion. Averaging the two often gives a more balanced measured estimate.
3) Why normalize the result to 1.73 m²?
Normalization adjusts for body surface area, making results easier to compare across people of different sizes or across repeated measurements when body size changes over time.
4) Can I use a collection that is not 24 hours?
Yes. The calculator accepts any timed duration greater than zero and converts the urine volume into a per-minute flow rate before calculating clearances.
5) Is urine volume alone enough to estimate clearance?
No. Urine volume is useful, but solute concentrations are needed to estimate urea and creatinine clearance. Volume alone does not show how much waste is being filtered.
6) Do urine and serum units need to match?
They should be entered using the correct unit selectors. This tool converts supported units internally, but both inputs must represent the same analyte type and collection context.
7) Can this calculator guide dialysis prescription changes?
It should support discussion, not replace clinical decision-making. Small collection errors, timing differences, and lab variation can materially change the measured result.
8) How should I review trends over time?
Use the same collection duration, similar sampling timing, and consistent units whenever possible. Comparing like-for-like measurements makes month-to-month trends more meaningful.