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Lab Test: Creatinine (Urine) Level

    Lab Test
    • Creatinine (Urine)
    Description
    • Measurement of urine creatinine along with serum creatinine to determine glomerular filtration rater (GFR)
    Reference Range
    • Males (20 to 29 years):  94-140 mL/min/1.73 m2 (0.91-1.35 mL/s/m2)
    • Females (20 to 29 years):  72-110 mL/min/1.73 m2 (0.69-1.06 mL/s/m2)
    • Males (30 to 39 years):  59-137 mL/min/1.73 m2 (0.57-1.32 mL/s/m2)
    • Females (30-39 years):  71-121 mL/min/1.73 m2 (0.68-1.17 mL/s/m2)
    • Note:  For each decade after the fourth decade in both sexes, values decrease approximately 6.5 mL/min based on 1.73 m2 body surface (0.06 mL/s per m2)
    • Infant (0 to 1 year:  72 mL/min/1.73 m2 (0.43 mL/s/m2)
    • Infant (1 year): 45 mL/min/1.73 m2 (0.43 mL/s/m2)
    • Infant (2 years): 55 mL/min/1.73 m2 (0.53 mL/s/m2)
    • Children (3 years): 60 mL/min/1.73 m2 (0.58 mL/s/m2)
    • Children (4 years):  71 mL/min/1.73 m2 (0.68 mL/s/m2)
    • Children (5 years):  73 mL/min/1.73 m2 (0.70 mL/s/m2)
    • Children (6 years):  64 mL/min/1.73 m2 (0.62 mL/s/m2)
    • Children (7 years):  67 mL/min/1.73 m2 (0.65 mL/s/m2)
    • Children (8 years):  72 mL/min/1.73 m2 (0.69 mL/s/m2)
    • Children (9 years):  83 mL/min/1.73 m2 (0.80 mL/s/m2)
    • Children (10 years):  89 mL/min/1.73 m2 (0.86 mL/s/m2)
    • Children (11 years):  92 mL/min/1.73 m2 (0.89 mL/s/m2)
    • Children (12 years):  109 mL/min/1.73 m2 (1.05 mL/s/m2)
    • Children (13 to 14 years):  86 mL/min/m2 (0.83 mL/s/m2)
    Indications & Uses
    • Suspected gout - increased creatinine clearance may indicate an increased glomerular filtration rate, and may be seen with a high-protein diet and hypercatabolic states
    • Suspected impaired renal function - Stages of chronic kidney disease and related GFRs expressed in mL/min/1.73 m2:
      • Stage 1:  kidney damage evident with abnormal or increased GFR - > 90
      • Stage 2:  kidney damage with a mild decrease in GFR - 60 to 89
      • Stage 3:  moderate decrease - GFR 30 to 59
      • Stage 4:  severe decrease - GFR 15 to 29
      • Stage 5:  renal failure - GFR < 15 or dialysis
    • Adults: 
      • Moderate renal impairment is described as a GFR of less than 60 mL/min/1.73 m2.
      • A persistently decreased GFR (< 60 mL/min/1.73 m2) along with proteinuria are important criteria used in chronic kidney disease to predict end stage renal disease.  
      • In the early stages of Type 1 diabetes, the GFR can be increased (greater than 130mL/min/1.73 m2) and is followed by persistent microalbuminuria, which as been associated with a 400% to 500% increase in the risk of progression to overt proteinuria and eventual end stage renal disease. 
      • Patients with type II DM may present with evidence of a decreased GFR ( less than 60 mL/min/1.73 m2) at the time of diagnosis. 
      • Diabetic patients (type 1 or 2) that have a normal to moderately decreased GFR (between 30 to 59 mL/min/1.73 m2; stages 1 through 3 of staging system) should be routinely monitored and treated to slow the progression of disease.  Renal replacement therapy is likely when the GFR is between 15 to 29 (stage 4).  A GFR of less than 15 or requirement for dialysis indicates a need for renal replacement therapy once uremia is present (stage 5).
    Clinical Application
    • A 24-hour urine collection is more physiologically complete than a spot collection because it accounts for the normal variations that can influence renal function.  However, studies have compared short- (e.g., 8 hour collections) and longer-duration urine creatinine clearance tests, and found similar results. 
    • Results decreased in:
      • Advanced age (i.e. greater than 80 years) - GFR can decrease at a rate of 13 mL/decade aft4er ages 45 to 50 years, acute and chronic renal failure, inadequate urine flow rate (i.e., due to dehydration or incomplete voiding), exercise, muscle wasting.
    • Results increased in:
      • Creatinine clearance can overestimate GFR by 10% to 20% at all levels of renal function, pregnancy (rises rapidly in early pregnancy and remains elevated until term; returns to normal quickly following delivery)
    • Other:
      • Gender (males have higher GFR, as compared to females), diet can influence renal function, and diurnal variation (i.e., GFR typically lower at night and highest in late morning).
    Procedure
    • Collect urine for 24 hours
    • Record patient's height and weight with urine sample
    • Collect serum/plasma at midpoint of urine collection period
    Storage and Handling
    • Store sample on ice or refrigerate during collection period
    • Refrigerate sample until laboratory analysis
    References
    • LaGow B et al., eds. PDR Lab Advisor. A Comprehensive Point-of-Care Guide for Over 600 Lab Tests.  First ed. Montvale, NJ: Thomson PDR; 2007.

MESH Terms & Keywords

  • Creatinine