102814 dry lab

Question 1

urine flow rate equals

Answer 1

urine volume/time of collection

Question 2

renal clearance of a substance equals

Answer 2

Cx= Ux * UF / Px

Ux= urine concentration of X
UF= urine flow rate
Px= plasma concentration of X

Question 3

free water clearance equals

Answer 3

UF - Cosm

Question 4

excretion rate of X equals

Answer 4

Ux * UF

Ux= urine concentration of X
UF = urine flow rate

Question 5

acetazolamide

Answer 5

carbonic anhydrase inhibitor that inhibits Na reabsorp in prox tubule

Question 6

acetazolamide’s effect on urine pH

Answer 6

pH becomes more basic (because bicarbonate is excreted)

Question 7

if urine flow doesn’t change for 2 hours and then starts to increase, what do you suspect?

Answer 7

there’s two counteracting agents like water and ADH

Question 8

if free water clearance becomes more positive by a lot, what do you suspect?

Answer 8

probably with taking a lot of free water so likely to be H2O or beer. beer inhibits ADH, so more positive free water clearance is probably from beer

Question 9

what should happen with taking in beef broth?

Answer 9

you need to get rid of more Na than water, so free water clearance should become more negative

Na excretion should increase

Question 10

what should happen with taking in a 30 mM sodium bicarbonate soln?

Answer 10

pH should increase

it’s 60 mM concentration in osmolarity, which is much lower than blood-so receiving a lot more H2O than solute. you need to get rid of extra water, so should have more positive free water clearance than an agent like acetazolamide that acts on proximal tubule which is isoosmotic

Question 11

fractional excretion of a substance =

Answer 11

urine excretion rate of substance/filtered load of glomerulus

it’s a measure of tubular fxn

Question 12

as tubular fluid moves from beginning to end of proximal tubule, creatinine concentration will

Answer 12

increase

Question 13

glomerulotobular balance

Answer 13

tubules reabsorb fixed percentage of filtered load. if filtered load increases, tubules will tend to still reabsorb the SAME percent

Question 14

which is usually higher: Uosm or Posm

Answer 14

Uosm

Question 15

free water clearance value is usually

Answer 15

negative

Question 16

pressure natriuresis

Answer 16

kidneys respond to change in BP by excreting sodium instead of reabsorbing it

Question 17

stimulation of renal sympath nerves will

Answer 17

increase sodium reabsorption
constrict blood vessels
retain sodium and fluid to prevent loss
decrease GFR (constrict vessels)

Question 18

GFR changes how in relation to serum creatinine?

Answer 18

as serum creatinine increases-at the lower end of serum creatinine, decreases in serum creatinine will cause larger changes in GFR

Question 19

equation for calculating GFR from serum creatinine

Answer 19

100/serum creatinine

Question 20

how can creatinine clearance be calculated to assess GFR?

Answer 20

UV/P

Cockcroft Gault eqn

Question 21

how can serum creatinine based GFR prediction be inaccurate?

Answer 21

extremes of age
BMI
diff in muscle mass (if pt is very heavy, will underestimate the GFR)

Question 22

what happens with ECF contraction/volume depletion?

Answer 22

decreased effective circulating volume
baroreceptor activation
increased sympath tone

see slide-angiotensin II, aldosterone, ADH(baroreceptor)

Question 23

in volume depletion, roles of angiotensin II and aldosterone?

Answer 23

angiotensin II likely has greater role because in proximal tubule, whereas aldosterone is in cortical collecting duct

Question 24

endocrine fxns of kidney

Answer 24

renin
erythropoetin
1,25 dihydroxyvitamin D (made in proximal tubule cells)

Question 25

chronic kidney disease produces what effects on calcium and phosphate

Answer 25

increases serum phosphorous (increased phosphorous retention)
decreases 1, 25 D (calcitriol)

both of these changes lead to decreased serum Ca

all of these changes lead to increased PTH, leading to increase bone turnover and extraosseous calcification