Biochemistry

Question 1

characteristics of an ideal marker of GFR

Answer 1

• appears at a constant rate
• freely filtered at glomerulus
• not reabsorbed from tubule
• not secreted by tubule
• does not undergo extra-renal elimination

Question 2

what makes inulin not an ideal GFR marker?

Answer 2

exogenous

not easy to measure

Question 3

how is ammonia (which is toxic) removed from the body?

Answer 3

it is converted to urea in the urea cycle

Question 4

what makes urea not an ideal GFR marker?

Answer 4

does not appear at a constant rate
reabsorbed from tubule
extra-renal elimination

Question 5

what is creatinine

Answer 5

product of muscle breakdown

Question 6

what reduces the effectiveness of creatinine as a GFR marker?

Answer 6

a small portion is secreted

varies between people

Question 7

what causes serum creatinine to vary between people?

Answer 7

age
sex
muscle mass
diet

Question 8

define clearance

Answer 8

volume of plasma cleared of substance per minute

Question 9

limitation of eGFR

Answer 9

not accurate at higher GFR so is reported as >60ml/min

Question 10

what is eGFR

Answer 10

this uses creatinine and age, sex, etc. (other factors) which would vary GFR

Question 11

GFR of stage 1 CKD

Answer 11

> 90ml/min/1.73m2

Question 12

GFR of stage 2 CKD

Answer 12

60-89ml/min/1.73m2

Question 13

GFR of stage 3 CKD

Answer 13

30-59ml/min/1.73m2

Question 14

GFR of stage 4 CKD

Answer 14

15-29ml/min/1.73m2

Question 15

GFR of stage 5 CKD

Answer 15

<15ml/min/1.73m2

Question 16

define nephrotic syndrome

Answer 16

kidneys pass too much protein into the urine due to damage to small blood vessels

Question 17

define microalbuminuria

Answer 17

excretion of albumin in abnormal quantities

often earliest expression of diabetic nephropathy

Question 18

define oliguria

Answer 18

low urine output

Question 19

define pre-renal AKI

Answer 19

reduced renal perfusion e.g. blood loss

Question 20

define renal AKI

Answer 20

intrinsic kidney tissue damage e.g. GN

Question 21

define post-renal AKI

Answer 21

ureteric obstruction e.g. calculi

Question 22

hormones that act on the kidney

Answer 22

ADH
PTH
aldosterone

Question 23

hormones the kidneys produce

Answer 23

erythropoietin
1,25-dihydroxycholecalciferol
renin

Question 24

biochemical presentation of pre-renal AKI

Answer 24

Na+ <20mmol/L
urea >10:1
osmolality >1.5:1

Question 25

biochemical presentation of renal AKI

Answer 25

Na+ >40mmol/L
urea <3:1
osmolality <1.1:1