Creatinine, Urine, and Creatinine Clearance, Urine, and Glomerular Filtration Rate (GFR)

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
Newborns15–60 mL
Infants
  3–10 days100–300 mL
  11–59 days250–450 mL
  2–12 mo400–500 mL
Children and adolescents
  13 mo–4 yr500–700 mL
  5–7 yr650–1,000 mL
  8–14 yr800–1,400 mL
Adults and older adults800–2,500 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
AgeConventional UnitsSI Units = (Conventional Units × 0.00884)
3–8 yr140–700 mg/24 hr1–6 mmol/day
9–12 yr300–1300 mg/24 hr3–12 mmol/day
13–17 yr500–2300 mg/24 hr4–20 mmol/day
Adult male1000–2500 mg/24 hr9–22 mmol/day
Adult female700–1600 mg/24 hr6–14 mmol/day
Adult male600–2100 mg/24 hr5–19 mmol/day
Adult female400–1400 mg/24 hr4–12 mmol/day
Random Urine Creatinine
Note: Laboratories may not report an established normal rangeConventional UnitsSI Units = (Conventional Units × 0.0884)
Adult male20–320 mg/dL1.77–28.3 mmol/L
Adule female20–275 mg/dL1.77–24.3 mmol/L
Creatinine ClearanceSI Units = (Conventional Units × 0.0167)
Children70–140 mL/min/1.73 m21.17–2.33 mL/s/1.73 m2
Adult male85–125 mL/min/1.73 m21.42–2.09 mL/s/1.73 m2
Adult female75–115 mL/min/1.73 m21.25–1.92 mL/s/1.73 m2
For each decade after 40 yrDecrease of 6–7 mL/min/1.73 m2Decrease 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.
AgeConventional Units
Less than 18 yrsNote: 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 yrsGreater than or equal to 60 mL/min/body surface area
Greater than 70 yrValues 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

There's more to see -- the rest of this topic is available only to subscribers.