Renal Function Tests Flashcards

0
Q

Waste product of creatine and phosphocreatine

A

Creatinine

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1
Q

Absorbs creatinine

A

Glomerulus

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2
Q

Removes creatinine

A

Kidneys

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3
Q

To which the amount of creatinine that is measured in blood is proportional

A

Patient’s lean muscle mass

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4
Q

Renal physiology

A

(Review)

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5
Q

Best substance to use for glomerular clearance

A

A chemical that is filtered completely through the glomerulus and not reabsorbed through the nephron tubule

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6
Q

Creatinine closely meets the criteria for a substance to be used flor glomerular clearance. Why?

A

1 Endogenous substance
2 Only around 10% pass through the tubules
3 Creatinine production is constant over time

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7
Q

Exogenous substance that must be introduced into the body that can be used for the evaluation of glomerular clearance

A

Inulin

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8
Q

Specimens used for Jaffe reaction

A

1 Serum
2 Plasma
3 Urine

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9
Q

Creatinine reference range: Male (Jaffe)

A

0.9-1.3 mg/dL

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10
Q

Creatinine reference range: Female (Jaffe)

A

0.6-1.1 mg/dL

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11
Q

Creatinine reference range: Children (Jaffe)

A

0.3-0.7 mg/dL

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12
Q

Jaffe reaction

A

Creatinine reacts with picric acid in an alkaline environment to generate an orange-red product

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13
Q

Generate orange-red color in Jaffe reaction

A
1 Protein
2 Glucose
3 Ascorbic acid
4 Acetone
5 Acetoacetate
6 Cephalosporins
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14
Q

Used to produce a measurable product that reflects creatinine concentration

A

1 Creatininase
2 Creatinase
3 Creatinine deaminase (used more frequently)

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15
Q

Factors that may affect creatinine clearance

A

1 Increased tubular reabsorption of creatinine
2 Reduced creatinine generation from muscle tissue
3 Dietary changes in nitrogenous compounds

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16
Q

Formula used for pediatric patients

A

Schwarz

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17
Q

Schwarz formula

A

Estimates creatinine clearance from serum creatinine

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18
Q

Creatinine reference range: Male (Schwarz)

A

95-130 mL/min

19
Q

Creatinine clearance reference range: Female (Schwarz)

A

80-120 mL/min

20
Q

Schwarz equation

A

Creatinine clearance = (k x Ht)Creat

Where 
k=0.45 if 1 year old
k=0.55 if 1-12 years old
Ht=height in cm
Creat=serum creatinine
21
Q

Cockcroft-Gault Equation

A
Creatinine clearance (mL/min)
= [(140-age) x wt(kg)]/[Serum creatinine (mg/dL) x 72]x0.85 for females
22
Q

Urinary protein methods

A

1 Turbidometric

2 Dye-binding

23
Q

Turbidometric method for urinary protein

A

Protein may be precipitated with sulfosalicylic afid, trichloroacetic acid or benzethonium chloride. The turbidity of the precipitate is measured photometrically.

24
Q

Dye-binding method for urinary protein

A

Dye binds to amino groups and the resulting color change is measured colorimetrically

25
Q

Urinary protein concentration

A

Urinary protein = [(urine protein concentration, mg/dL) x urine volume, dL]/day

26
Q

Urinary protein test

A

1 A 12- or 24-hour (preferred, variations) collection may be used
2 Urine should be collected as describe for creatinine clearance
3 Urine should be kept cool

27
Q

Acute glomerular nephritis

A

1 Sudden onset of hematuria and proteinuria
2 Decrease in glomerular filtration rate
3 Rise in plasma creatinine
4 Fall in creatinine clearance

28
Q

Waste product of the degradation of amino acids into CO2 and ammonia

A

Urea

29
Q

Azotemia

A

Excess of urea

30
Q

Physiology of urea

A

1 Urea is synthesized in the liver
2 It is transported through blood to the kidney, where it is filtered through the glomerulus
3 Almost half of the urea is reabsorbed back into the blood by passive transport in the nephron tubule

31
Q

Factors increasing BUN:Creatinine ratio

A

1 Prerenal
2 Renal
3 Postrenal

32
Q

Reference range for BUN:Creatinine ratio

A

10:1 to 20:1

33
Q

Methods for measuring the concentration of urea

A

1 Urease method

2 Colorimetric method

34
Q

Specimen for urea

A

1 Serum
2 Plasma

Anticoagulants containing fluoride or citrate should not be used

35
Q

Reference range of urea

A

Serum or plasma 6-20 mg/dL

36
Q

Reaction principle for urease method

A

Urea + H2O – (urease) > 2NH4+ +HCO3-

37
Q

Measurement of ammonia liberated (urease methods)

A

1 The reaction may be coupled with a reaction that drives NADH to NAD+
2 The conductivity of the ammonium ion may be measured
3 The Berthelot reaction may be used
NH4+ + NaOCl + phenol – (nitroprusside) > indophenol
4 An indicator dye may be used
5 The reaction may be coupled with another that produces H2O2

38
Q

Principle of colorimetric method for urea

A

The diacetyl monoxime reaction is used to produce a color change

Diacetyl monoxime + urea – (acid) > diazine (yellow compound)

39
Q

Specimen for urinary microalbumin test

A

1 A 12- or 24-hour (preferred, variations) collection may be used
2 Urine should be collected as described for creatinine clearance
3 Urine should be kept cool

40
Q

Indicative of microalbuminuria

A

Excretion of 30 to 300 mg of albumin per 24-hour period on two of three collections

41
Q

Urinary microalbumin test equation

A

(Urine albumin concentration, mg/dL x urine volume, dL)/day

42
Q

Reaction principle of microalbumin test

A

Dye binds to albumin and causes a shift in the maximum absorption.

43
Q

Dyes used in urinary microalbumin test

A

1 Methyl orange
2 Bromcresol green
3 Bromcresol purple

44
Q

Notes on urinary microalbumin test

A

1 Tests for microalbuminuria must be sensitive to low concentrations of albumin.
2 Urinalysis dipsticks measure protein through the effects of protein on pH; these techniques are not sensitive to low concentrations of albumin in the urine.
3 Semiquantitative immunologic methods screen for low concentrations of albumin.
4 Positive semiquantitative results must be confirmed by a qualitative method.