I. Indications

  1. Creatinine Clearance estimates GFR

II. Interpretation: Normal Creatinine Clearance

  1. Men
    1. Average: 120 ml/min/1.73 m2 (+/-25) or 175 Liters/day
    2. Range: 97-137 ml/min/1.73 m2 (0.93-1.32 ml/sec/m2 IU)
  2. Women
    1. Average: 95 ml/min/1.73 m2 (+/-20) or 135 Liters/day
    2. Range: 88-128 ml/min/1.73 m2 (0.85-1.23 ml/sec/m2 IU)

III. Calculation: Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)

  1. Calculation
    1. Males: 141 * min (sCr/0.9 or 1) ^ -0.411 * max(sCr/0.9 or 1)^ - 1.209 * 0.993 ^ ageY
    2. Females: 141 * min (sCr/0.7 or 1) ^ -0.329 * max(sCr/0.7 or 1)^ - 1.209 * 0.993 ^ ageY * 1.018
    3. Black: Multiply above equation (based on gender) by 1.159
  2. Annotation
    1. Where sCr is Serum Creatinine
    2. Min is the minimum value (either that calculated or 1)
    3. Max is the maximum value (either that calculated or 1)
    4. Where ^ represents to the power of...
  3. Efficacy
    1. More accurate than either CKD or MDRD
  4. References
    1. Levey (2009) Ann Intern Med 150(9): 604-12

IV. Calculation: Cockcroft-Gault formula for GFR estimate

  1. Indications: Stable Kidney function
    1. Older patients
    2. General screening
  2. Male GFR = (140 - age) x (weight) / (sCr x 72)
  3. Female GFR = (140 - age) x (weight) x 0.85 / (sCr x 72)
  4. Annotation
    1. Where GFR is Glomerular Filtration Rate in ml/min
    2. Where age is in years
    3. Where weight is Lean Body Mass in kilograms
    4. Where sCr is Serum Creatinine in mg/dl
  5. Efficacy
    1. As accurate as 24 hour urine in most cases
    2. Exceptions: See 24 hour CrCl indications below
  6. Resources: GFR Calculator
    1. http://www.kidney.org/kls/professionals/

V. Calculation: Abbreviated MDRD Study Equation

  1. Indications: Chronic Kidney Disease, stable function
    1. Middle aged patients
    2. Black patients
    3. Diabetic Nephropathy
    4. Status-post Kidney transplant
  2. Efficacy
    1. More accurate than Cockroft-Gault in CRF
      1. Levey (1999) Ann Intern Med 130:461-70
    2. Overestimates Chronic Kidney Disease when used as a general screening tool
      1. Underestimates GFR in the absence of Kidney disease
      2. Rule (2004) Ann Intern Med 141:929-37
  3. Formula: GFR = 186 x (sCr)^-1.154 x (age)^-0.203
    1. Where sCr is raised by power of -1.154
    2. Where age is raised by power of -0.203
  4. Modifiers
    1. Female: Multiply GFR by 0.742
    2. Black: Multiply GFR by 1.210
  5. Annotation
    1. Where GFR=Glomerular Filtration Rate ml/min/1.73 m2
    2. Where sCr is Serum Creatinine in mg/dl

VI. Calculation: 24 hour Creatinine Clearance

  1. Previously considered gold standard GFR evaluation
    1. Now thought to be less accurate than calculations (see above) due to flawed collection
  2. Indications
    1. Pregnancy
    2. Severely underweight or Overweight
    3. Very young and very old
    4. Malnutrition
    5. Skeletal muscle disorders, paraplegia, quadriplegia
  3. Formula
    1. CrCl = (uCr x uV) / (sCr x 1440)
  4. Annotation
    1. Where CrCl is Creatinine Clearance in ml/min
    2. Where uCr is Urine Creatinine in mg/dl
    3. Where sCr is Serum Creatinine in mg/dl
    4. Where uV is 24 hour urine volume in ml
    5. Where 1440 represents number of minutes in 24 hours
  5. Indications (where calculation above is inaccurate)
    1. Altered protein intake
      1. Vegetarian diet
      2. Creatine Supplementation
    2. Altered muscle mass
      1. Malnutrition or muscle wasting
      2. Amputation

VII. Interpretation: Increased GFR

  1. Pregnancy
  2. Exercise

VIII. Interpretation: Decreased GFR

  1. Chronic Kidney Disease or Renal insufficiency
  2. Advanced age
    1. Normal GFR is 125 ml/min/1.73 m2 at age 30 years
    2. GFR decreases by 1 ml/min/year over age 30 years
  3. Inadequate urine specimen collection
    1. See Urine Creatinine for judging adequacy
  4. Medications (Decrease tubular secretion of Creatinine)
    1. Cimetidine
    2. Procainamide
    3. Antibiotics
    4. Quinidine

IX. Precautions: Pitfalls

  1. Calculating GFR in specific cohorts
    1. Overweight (GFR >25 kg/m2)
      1. Calculate based on adjusted body weight
      2. Adjusted body weight = wtKgIdeal + 0.4 * (wtKgActual - wtKgIdeal)
    2. Underweight
      1. Use actual weight
      2. Do not round up to Serum Creatinine (significantly underestimates GFR)
    3. Elderly
      1. Do not round up to Serum Creatinine (significantly underestimates GFR)
    4. Amputation
      1. Measure 24 hour Creatinine Clearance
  2. Creatinine Clearance (by 24 hour urine) is overestimated at decreased GFR
    1. As GFR decreases, secreted Creatinine makes up larger percentage of total Urine Creatinine
    2. Consider pre-medicating the 24 hour Urine Collection
      1. Give Cimetidine or Trimethoprim for 2 days prior to 24 hour Urine Collection
      2. Overcomes the over-estimatation of GFR

Images: Related links to external sites (from Google)

Calculation (SoapNote.org)

Calculation (SoapNote.org)

Ontology: Glomerular Filtration Rate (C0017654)

Definition (NCI) A kidney function test that measures the fluid volume that is filtered from the kidney glomeruli to the Bowman's capsule per unit of time.
Definition (NCI) A kidney function test that measures the fluid volume that is filtered from the kidney glomeruli to the Bowman's capsule per unit of time.
Definition (MSH) The volume of water filtered out of plasma through glomerular capillary walls into Bowman's capsules per unit of time. It is considered to be equivalent to INULIN clearance.
Definition (CSP) rate at which plasma is filtered by the glomerular filtration membrane into Bowman's space; determined by the permeabiliy of the membrane, hydrostatic pressure in the glomerular capillaries and Bowman's space, and the colloid osmotic pressure exerted by the proteins of the capillary plasma.
Concepts Diagnostic Procedure (T060)
MSH D005919
SnomedCT 80274001
English Filtration Rate, Glomerular, Filtration Rates, Glomerular, Glomerular Filtration Rates, Rate, Glomerular Filtration, Rates, Glomerular Filtration, Glomerular filtration rate, NOS, glomerular filtration rate, GFR, gfr, rate filtration glomerular, filtration glomerular rate, Glomerular filtration rate, Glomerular filtration rate (observable entity), Glomerular filtration rate (function), Glomerular filtration rate, function (observable entity), Glomerular Filtration Rate
Italian Velocità di filtrazione glomerulare, Filtrato glomerulare renale, Percentuale di filtrato glomerulare
Dutch GFR, glomerulaire filtratiesnelheid, Filtratiesnelheid, glomerus-, Glomerusfiltratiesnelheid
French TFG (taux de filtration glomérulaire), TFG (Taux de Filtration Glomérulaire), Taux de filtration glomérulaire, Débit de filtration glomérulaire
German GFR, glomerulaere Filtrationsrate, Glomeruläre Filtrationsrate
Portuguese Taxa de filtração glomerular, Fracção de filtração glomerular, Taxa de Filtração Glomerular
Spanish TFG, tasa de filtración glomerular (entidad observable), tasa de filtración glomerular (función), tasa de filtración glomerular, Tasa de filtración glomerular, Tasa de Filtracion Glomerular, Tasa de Filtración Glomerular
Japanese 糸球体濾過率, GFR, シキュウタイロカリツ, GFR
Swedish Glomerulär filtrationshastighet
Czech glomerulární filtrace - hodnota, Glomerulární filtrace, GFR
Finnish Glomerulusten suodattumisnopeus
Russian KLUBOCHKOVOI FIL'TRATSII SKOROST', POCHECHNYKH KLUBOCHKOV FIL'TRATSII SKOROST', КЛУБОЧКОВОЙ ФИЛЬТРАЦИИ СКОРОСТЬ, ПОЧЕЧНЫХ КЛУБОЧКОВ ФИЛЬТРАЦИИ СКОРОСТЬ
Croatian GLOMERULARNA FILTRACIJA
Polish Współczynnik filtracji kłębuszkowej, Wielkość przesączania kłębuszkowego, GFR, Wskaźnik filtracji kłębuszkowej
Hungarian Glomeruláris filtrációs ráta, GFR

Ontology: CREATININE CLEARANCE QUANTITATIVE TRAIT LOCUS (C1846718)

Concepts Disease or Syndrome (T047)
English CRCL, CREATININE CLEARANCE QUANTITATIVE TRAIT LOCUS