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AUBF > Renal Physiology and Renal Function Tests (2) > Flashcards

Renal Physiology and Renal Function Tests (2) Flashcards

1
Q

Measures the rate at which the kidneys can remove or clear a filterable substance from the blood

  • Checks how fast the kidney removes a marker from the blood.
A

Clearance Test

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2
Q

Clearance test that requires a marker – should have specific characteristics;

A
  • removal of a substance from plasma into urine over a fixed period,
  • not bound to proteins,
  • filtered, neither reabsorbed nor secreted
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3
Q

Markers of the clearance test

A
  • Exogenous substance (administered)
  • Endogenous substance (natural in the body)
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4
Q

High clearance test =

A

efficient excretion

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5
Q

Low clearance test =

A

inefficient excretion

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6
Q

Normal Value: Creatinine Clearance
in Female

A

75 - 112 ml/min

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7
Q

Normal Value: Creatinine Clearance in Male

A

85 - 125 ml/min

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8
Q

expected to have a higher muscle mass and higher body surface area why their normal values are higher

A

Male

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9
Q

Markers administered/ injected to patients

A

EXOGENOUS

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10
Q
  • Reference method***
  • Not routinely done because exogenous
  • Soluble, freely filtered, neither secreted, nor reabsorbed
A

Inulin

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11
Q

127mL/min/1.73m2

A

Male inulin

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12
Q

118 ml/min/1.73m2

A

Female inulin

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13
Q
  • 125I-iothalamate
  • 99m Tc-DTPA
  • Iohexol
  • 51Cr-EDTA
A

Radioactive Markers

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14
Q

Creatinine: Ccrea

A

ENDOGENOUS

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15
Q

waste product of muscle metabolism that is produced enzymatically by creatine phosphokinase from creatine

  • 113 Da
  • Most widely used marker for GFR
  • Produced constantly
  • Not bound to proteins
  • Not reabsorbed
  • Minimally secreted
A

Creatinine

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16
Q
  1. Some creatinine is secreted by the tubules
  2. Chromogens in plasma react in the chemical analysis
  3. Medications inhibit tubular secretion
  4. Bacteria break down urinary creatinine
  5. A diet heavy in meat can raise creatinine
  6. Not a reliable indicator in patients suffering from musclewasting diseases
  7. Depends on the completeness of a 24-hour collection
  8. It must be corrected for Body Surface Area (unless normal)
A

CREATININE CLEARANCE: DISADVANTAGES

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17
Q

Methods that do not require the collection of timed (24-hour) urine specimens: (blood)

A
  • Estimated glomerular filtration rate eGFR using serum creatinine
  • Cystatin C
  • Beta2-microglobulin
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18
Q
  • Variables - age, sex, weight in kg
  • Female - multiply answer by 0.85
  • Females are expected to have a lower body mass
A

Cockcroft & Gault

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19
Q

Six variables: age, sex, serum urea nitrogen, serum creatinine, race, and serum albumin

Simplified MDRD based on four variables: serum creatinine, age, race, and sex

  • Serum creatinine obtained with an enzymatic IDMStraceable assay (method to quantify serum creatinine)
  • Correspond more closely to the isotope dilution mass spectrophotometry (IDMS)
A

Modification of Diet in Renal Disease (MDRD)

20
Q

traceable formula- recommended by the
National Kidney Disease Education Program (NKDEP)

A

Modification of Diet in Renal Disease
MDRD-IDMS

21
Q

IDMS

A

isotope dilution mass
spectrophotometry

22
Q

MDRD

A

Modification of Diet in Renal Disease

23
Q

CKD-EPI

A

Chronic Kidney Disease Epidemiology Collaboration

24
Q

Estimates GFR from serum creatinine, age, sex, and race

A

CKD-EPI

25
Q
  • Major end product of protein and amino acid metabolism
  • Freely filtered by the glomeruli but variably reabsorbed by the
    tubules
  • Not preferred
A

UREA CLEARANCE: ENDOGENOUS

26
Q
  • For screening and monitoring GFR
  • Small protein (M.W. = 13,359)
A

CYSTATIN C

27
Q
  • Produced at a constant rate by all nucleated cells
  • Readily filtered by glomerulus
  • Reabsorbed and broken down by the RTEs
  • Not secreted by the tubules
  • Serum concentration can be directly related to GFR
A

CYSTATIN C

28
Q
  • Molecular weight - 11,800
  • Dissociates from human leukocyte antigens at a constant
    rate
  • Rapidly removed from the plasma by GF
  • Enzyme immunoassay
  • Increased beta2- macroglobulin: decreased GFR
A

BETA2-MICROGLOBULIN

29
Q
  • Depends on the number of functioning nephrons and the functional capacity of these nephrons
A

GFR

30
Q
  • Determines the extent of nephron damage
  • Monitors the effectiveness of treatment
  • Determines the feasibility of administering medications
A

GFR Clinical Significance

31
Q
  • Most common test; popular
  • Specific gravity: number and density
A

Specific Gravity

32
Q
  • Patients are deprived of fluids for 24 hrs prior to measuring the specific gravity; obsolete
A

Fishberg Test

33
Q
  • Compares the volume and specific gravity of day and night samples; obsolete
A

Mosenthal Test

34
Q

Serum osmolality:

A

: 275 to 300 mOsm

35
Q

number of particles in a solution
* Better than specific gravity as it is more specific
* Renal concentration is concerned with small particles
* Large MW molecules do not contribute to the evaluation of
renal concentration

A

Osmolality

36
Q

INSTRUMENTS FOR MEASUREMENT OF OSMOLALITY

A

Freezing point Osmometers and Vapor Pressure Osmometers

37
Q

Measurement of freezing point depression

A

Freezing point Osmometers

38
Q
  • No ability/ capacity to release ADH
  • Unable to stimulate hypothalamus to release ADH; problem
    with hormones
A

Neurogenic Diabetes Insipidus

39
Q
  • ADH is present but kidney is unresponsive to AD
A

Nephrogenic Diabetes Insipidus

40
Q

To check Diabetes Insipidus:
* Deprive patient of water for

A

12 hrs

41
Q
  • Restrict fluid for another two hours
  • Collect urine and serum for osmolality testing
A

If < 800 mOsm

42
Q

If the osmolality normalizes then there is a _____

A

neurogenic
diabetes insipidus

43
Q

If the osmolality decreases then there is a_____

A

nephrogenic diabetes insipidus

44
Q
  • Volume of blood plasma that is cleared of solute-free water per unit time
  • To determine ability of the kidneys to respond to the state of body hydration
A

Free Water Clearance

45
Q

indicates how much water must be
cleared each minute to produce a urine with the same osmolarity as the plasma

A

Osmolar clearance

AUBF (12 decks)

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