Vanders Renal Ch3

Question 1

Define the term clearance in a biomedical context

Answer 1

The volume of plasma per unit time from which all of a specific substance is removed

Question 2

What is metabolic clearance rate?

Answer 2

The quantitative measure of how a substance is removed from the plasma by any of the body’s mechanisms

Question 3

Differentiate between general clearance and specific renal clearance

Answer 3

General clearance refers to removal by any means, while renal clearance is specifically by the kidneys

Question 4

What information is required to calculate clearance?

Answer 4

Plasma concentration of the substance, urine concentration, and urine flow rate

Question 5

What criteria must a substance meet to be used as a measure of glomerular filtration rate (GFR)?

Answer 5

The substance must be freely filtered, not reabsorbed or secreted

Question 6

Which substances are commonly used to measure GFR?

Answer 6

Inulin and creatinine

Question 7

What is the significance of inulin clearance?

Answer 7

It specifically indicates renal clearance and is used to measure GFR

Question 8

Calculate the clearance of a substance given its excretion rate and plasma concentration

Answer 8

Clearance (Cx) = Excretion rate (Ux * V) / Plasma concentration (Px)

Question 9

What does a clearance greater than GFR indicate?

Answer 9

Net secretion of the substance

Question 10

What does a clearance less than GFR indicate?

Answer 10

Net reabsorption of the substance

Question 11

What is the gold standard for measuring GFR?

Answer 11

Inulin clearance

Question 12

What is the common method to measure GFR in patients?

Answer 12

Creatinine clearance

Question 13

Why does creatinine clearance slightly overestimate GFR?

Answer 13

A small amount of creatinine is secreted by the proximal tubule

Question 14

What is the relationship between plasma creatinine concentration and GFR?

Answer 14

They vary inversely; as GFR decreases, plasma creatinine increases

Question 15

Fill in the blank: Plasma concentration of _______ is a practical indicator of GFR.

Answer 15

creatinine

Question 16

True or False: All substances used to measure GFR must be reabsorbed by the kidneys.

Answer 16

False

Question 17

What is the role of cystatin C in estimating GFR?

Answer 17

Cystatin C is produced at a constant rate and is cleared by glomerular filtration, reflecting GFR

Question 18

What is the typical plasma concentration of creatinine in a healthy person?

Answer 18

About 1 mg/dL

Question 19

What happens to plasma creatinine concentration if GFR decreases by 50%?

Answer 19

Plasma creatinine stabilizes at 2 mg/dL

Question 20

What is the significance of the clearance units?

Answer 20

They are expressed as volume per time, reflecting the volume of plasma cleared of a substance

Question 21

Describe the renal handling of inulin

Answer 21

Inulin is freely filtered, not reabsorbed or secreted, and all filtered inulin appears in the urine

Question 22

What does the clearance of para-aminohippurate (PAH) indicate?

Answer 22

It indicates effective renal plasma flow, as PAH is filtered and secreted

Question 23

What does a clearance equal to GFR indicate?

Answer 23

No net reabsorption or secretion has occurred

Question 24

What are some exogenous agents used to measure GFR?

Answer 24

125I-iothalamate, 59Cr-EDTA, 99mTc-DTPA

Question 25

What is the advantage of using cystatin C over creatinine for GFR estimation?

Answer 25

Cystatin C is less affected by muscle mass and is cleared more completely

Question 26

What does clearance express in the context of renal function?

Answer 26

The rate at which a substance is removed from the plasma and excreted in the urine

Question 27

What is the best measure of GFR?

Answer 27

Inulin clearance

Question 28

Which clearance can be used as an estimate of renal blood flow?

Answer 28

Para-aminohippurate clearance

Question 29

What is a practical measure of GFR?

Answer 29

Creatinine clearance

Question 30

Which two substances are clinically used as indicators of GFR?

Answer 30

* Plasma creatinine concentration * Cystatin C

Question 31

What is renal scintigraphy used for?

Answer 31

Assessing the function of each kidney separately

Question 32

Fill in the blank: Renal clearance of any substance is calculated by a _______.

Answer 32

clearance formula relating urine flow to urine and plasma concentrations

Question 33

What happens to plasma creatinine levels when GFR is reduced?

Answer 33

Plasma creatinine stabilizes at a higher concentration

Question 34

True or False: Cystatin C levels are less affected by age, sex, race, and muscle mass than creatinine levels.

Answer 34

True

Question 35

What is the significance of an increasing plasma creatinine over time?

Answer 35

It is a red flag that there may be a renal problem

Question 36

What is the effect of large amounts of red meat on creatinine levels?

Answer 36

It may cause a transient increase in creatinine levels

Question 37

What can MAG3 clearance indicate about kidney function?

Answer 37

Deficient clearance indicates poor ability to clear creatinine and other organic waste

Question 38

What does a renogram plot represent?

Answer 38

Graphical plot of radioactive counts versus time

Question 39

What is the typical peak time for healthy kidneys in renal scintigraphy?

Answer 39

3 to 4 minutes

Question 40

What is the expected plasma urea concentration after 80% nephron destruction if initial concentration was 5 mmol/L?

Answer 40

25 mmol/L

Question 41

What is the relationship between MAG3 clearance and creatinine clearance?

Answer 41

MAG3 clearance is highly correlated with creatinine clearance

Question 42

Fill in the blank: Cystatin C measurements have not been shown to be superior to _______.

Answer 42

formula-adjusted estimations of kidney function based on creatinine measurements

Question 43

What factors are included in eGFR equations?

Answer 43

* Age * Body size * Gender * Race

Question 44

True or False: Urea measurement is a more accurate indicator of GFR than plasma creatinine or cystatin C.

Answer 44

False

Question 45

What does the clearance formula relate to?

Answer 45

Urine flow to urine and plasma concentrations

Question 46

What does a slower rise in kidney counts during renal scintigraphy indicate?

Answer 46

Poor kidney performance

Question 47

What substance is cleared by the kidneys almost exclusively by secretion?

Answer 47

MAG3