Evaluation of Renal Function- Dr. Heeter

What are the top 3 causes of renal impairment in the population?

1. DM

2. HTN

3. Glomerulonephritis

The National Kidney Foundation recommends _______ urinalysis for all patients with CKD.

a. yearly

b. monthly

c. weekly

d. seasonally

a - yearly

What is the normal albumin to creatinine ratio?

<30 mg albumin (<200 mg protein) : 1 gm creatinine

Microalbuminuria is described by what albumin to creatinine ratio?

30-300 mg per 1 gm of creatinine

Macroalbuminuria is described by what albumin to creatinine ratio?

> 300 mg per 1 gm of creatinine

What leads to decreased BUN excretion?

a. malnourishment

b. dehydration

c. urea

d. SCr

b - dehydration

An elevated BUN:SCr ratio indicates that there is __________ effective circulating volume.

a. decreased

b. increased

a - decreased

What is our primary/standard marker for the detection of kidney disease?

Serum Creatinine

This is another marker of renal function. It’s not common, however it’s helpful because it is not dependent on muscle mass like SCr, instead is produced by all cells in the body.

Cystatin C

What is the best indicator of functional renal mass?

GFR

What is the normal GFR in a healthy woman?

118± 20 mL/min/1.73 m²

What is the normal GFR in a healthy man?

127± 20 mL/min/1.73 m²

What is the gold standard for measuring GFR?

Inulin

Equation for CrCl

CrCl= (Ucr*V)/ Pcr

MDRD 6 and 4 variable equations are used ONLY FOR WHAT?

• staging chronic kidney disease

MDRD equations estimate what value?

GFR

What equation is used for drug dosing adjustments and estimates Creatinine Clearance?

Cockcroft- Gault Equation

What is the Cockcroft- Gault equation?

CrCl (mL/min) =

For females what is the result of the Cockcroft- Gault equation multiplied by?

0.85

List the equations for IBW for male and female:

List the equation for Adjusted Body Weight:

If the actual weight < IBW, what weight is used in the Cockcroft- Gault Equation?

use actual weight

If the actual weight is between 100-130% IBW, what weight is used in the Cockcroft- Gault Equation?

use IBW

If a patient is obese, what weight is used in the Cockcroft- Gault Equation?

adjusted body weight

What estimation of Creatinine Clearance is best for obese patients?

Salazar-Corcoran equation

True or False: CKD- EPI CR has been shown to be more accurate then CKD- EPI CYS.

False- one has not been shown to be more accurate than the other

True or False: CKD- EPI CR-CYS has been shown to be more accurate than CKD- EPI CYS and CKD- EPI CR.

true

Are MDRD and CKD-EPI equation good equations to use for dose adjustments?

No - MDRD and CKD- EPI equations are eGFR equations, NOT estimates of CrCl. Drug dose adjustments are made off of CrCl levels.

For estimating CrCl in elderly patients, what are 2 things to make sure you don’t do?

• round down

  • rounding down can lead to underdosing of meds

• round up

  • proven less accurate

What equation is used to calculate GFR/CrCl in infants?

Schwartz equation

The Schwartz equation is used for children under the age of ____.

3

What equation shows the best estimate of CrCl in patients 3-19 years old?

Cockroft Gault Equation

Patients under 5 feet tall should use this equation and if significantly shorter should use this equation.

• CG if short

• Jeliffe if signficantly shorter

Summary: Select the right equation for each of the statements.

1. For drug dosing

2. For obese patients

3. Children under 3

4. Elderly patients

5. CKD Staging

1. Cockcroft Gault

2. Adjusted weight for Cockcroft Gault equation, Salazar-Corcoran equation

3. Schwartz equation

4. Cockroft Gault using measured SCr

5. MDRD, CKD-EPI, or CG may be used

Calc a CrCl for the following patient using the Cockroft- Gault Equation:

• 82-year-old female

• Ht: 66"

• Wt: 62 kg

• SCr: 1.2 mg/dL

1. Calculate Ideal Body Weight

   • Pay attention to gender

   • IBW= 59.3

2. Decide whether to use Actual weight, IBW, or need to find adjusted body weight

   • Actual weight btwn 100-130% of IBW so use IBW

3. Calculate CrCl

   • make sure to multiply by 0.85 because this is a female

4. Answer: 34 ml/min