Creatinine, Urine, and Creatinine Clearance, Urine
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Synonym/Acronym:
N/A
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:
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| 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. | |||||||||||||||||||||||||||||||||||||||||
| Urine Creatinine | |||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Age | Conventional Units | SI Units | |||||||||||||||||||||||||||||||||||||||
| Urine Creatinine (Conventional Units × 8.84) | |||||||||||||||||||||||||||||||||||||||||
| 2–3 yr | 6–22 mg/kg/24 hr | 53–194 micromol/kg/24 hr | |||||||||||||||||||||||||||||||||||||||
| 4–18 yr | 12–30 mg/kg/24 hr | 106–265 micromol/kg/24 hr | |||||||||||||||||||||||||||||||||||||||
| Adult male | 14–26 mg/kg/24 hr | 124–230 micromol/kg/24 hr | |||||||||||||||||||||||||||||||||||||||
| Adult female | 11–20 mg/kg/24 hr | 97–177 micromol/kg/24 hr | |||||||||||||||||||||||||||||||||||||||
| Creatinine Clearance | |||||||||||||||||||||||||||||||||||||||||
| Creatinine Clearance (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 | 1.42–2.08 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. | |||||||||||||||||||||||||||||||||||||||||
Critical Findings and Potential Interventions
- Degree of impairment:
- Borderline: 62.5–80 mL/min/1.73 m2 (SI: 1–1.3 mL/s/1.73 m2)
- Slight: 52–62.5 mL/min/1.73 m2 (SI: 0.9–1 mL/s/1.73 m2)
- Mild: 42–52 mL/min/1.73 m2 (SI: 0.7–0.9 mL/s/1.73 m2)
- Moderate: 28–42 mL/min/1.73 m2 (SI: 0.5–0.7 mL/s/1.73 m2)
- Marked: Less than 28 mL/min/1.73 m2 (SI: Less than 0.5 mL/s/1.73 m2)
Timely notification to the requesting health-care provider (HCP) of any critical findings and related symptoms is a role expectation of the professional nurse. A listing of these findings varies among facilities.
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