Creatinine, Urine, and Creatinine Clearance, Urine, and Glomerular Filtration Rate (GFR)
General
General
General
Synonym/Acronym:
CrCl, eGFR
Rationale
To assess and monitor kidney function related to acute kidney injury or chronic kidney disease.
Patient Preparation
There are no fluid or medication restrictions unless by medical direction. Instruct the patient to refrain from eating meat during the test and to refrain from excessive exercise for 8 hr before the test. Protocols may vary among facilities. Usually, a 24-hr urine collection is ordered. As appropriate, provide the required urine collection container and specimen collection instructions.
Normal Findings
Method: Spectrophotometry.
| Normal Urine Volume per 24 hr |
These ranges are very general averages and were not calculated on the basis of normal average body weights. Literature shows that expected urinary output can be estimated by a formula in which the expected output is as follows: - Infants: 1–2 mL/kg/hr
- Children and adolescents: 0.5–1 mL/kg/hr
- Adults and older adults: 1 mL/kg/hr
|
| Newborns | 15–60 mL |
| Infants | |
| 3–10 days | 100–300 mL |
| 11–59 days | 250–450 mL |
| 2–12 mo | 400–500 mL |
| Children and adolescents | |
| 13 mo–4 yr | 500–700 mL |
| 5–7 yr | 650–1,000 mL |
| 8–14 yr | 800–1,400 mL |
| Adults and older adults | 800–2,500 mL (average 1,200 mL) |
| Normally, more urine is produced during the day than at night. With advancing age, the reverse often occurs. The total expected outcome for adults appears to remain the same regardless of age. |
| Timed Urine Creatinine |
|---|
| Age | Conventional Units | SI Units = (Conventional Units × 0.00884) |
| 3–8 yr | 140–700 mg/24 hr | 1–6 mmol/day |
| 9–12 yr | 300–1300 mg/24 hr | 3–12 mmol/day |
| 13–17 yr | 500–2300 mg/24 hr | 4–20 mmol/day |
| Adult male | 1000–2500 mg/24 hr | 9–22 mmol/day |
| Adult female | 700–1600 mg/24 hr | 6–14 mmol/day |
| Adult male | 600–2100 mg/24 hr | 5–19 mmol/day |
| Adult female | 400–1400 mg/24 hr | 4–12 mmol/day |
| Random Urine Creatinine |
| Note: Laboratories may not report an established normal range | Conventional Units | SI Units = (Conventional Units × 0.0884) |
| Adult male | 20–320 mg/dL | 1.77–28.3 mmol/L |
| Adule female | 20–275 mg/dL | 1.77–24.3 mmol/L |
| Creatinine Clearance | SI Units = (Conventional Units × 0.0167) |
| Children | 70–140 mL/min/1.73 m2 | 1.17–2.33 mL/s/1.73 m2 |
| Adult male | 85–125 mL/min/1.73 m2 | 1.42–2.09 mL/s/1.73 m2 |
| Adult female | 75–115 mL/min/1.73 m2 | 1.25–1.92 mL/s/1.73 m2 |
| For each decade after 40 yr | Decrease of 6–7 mL/min/1.73 m2 | Decrease of 0.06–0.07 mL/s/1.73 m2 |
| The 24-hr urine volume is recorded and provided with the results of the creatinine measurement. |
| Estimated Glomerular Filtration Rate (eGFR) Many laboratories now report eGFR with creatinine clearance. |
| Age | Conventional Units |
| Less than 18 yrs | Note: The eGFR equation generally recommended for individuals under 18 yrs of age is the Bedside Schwartz formula and is based on Cr levels and height in centimeters. |
| 18–70 yrs | Greater than or equal to 60 mL/min/body surface area |
| Greater than 70 yr | Values in older adults remain relatively stable, after a period of decline related to loss of muscle mass during the transition from adult to older adult. |
Critical Findings and Potential Interventions
N/A
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