renal

Question 1

can be used to calculate GFR
because it is freely fltered and is neither
reabsorbed nor secreted

Answer 1

Inulin

Question 2

how much liquid goes into the filter

Answer 2

Glomerular Filtration Rate

Question 3

how much liquid does the kidney handle

Answer 3

Renal Plasma Flow

Question 4

Of all the substance X is entering the kidney, what % gets filtered

Answer 4

Filtration Fraction

Question 5

how much of each blood component is being removed

Answer 5

Renal Clearance

Concept:

In 1L of blood, there is 5g of sodium. the kidney excretes 5g of sodium per 1 L of blood

Question 6

how do you solve for Renal Clearance?

Answer 6

Clearance of substance x = concentration of substance x in urine * volume flow (L/min)
_________________
concentration of substance x in plasma

Question 7

what given would you need to solve clearance of a solute

Answer 7

plasma concentration
urine concentration
plasma flow

Question 8

why is inulin used to measure GFR

Answer 8

inulin is neither secreted nor absorbed

meaning, inulin (which is artificial and introduced into the body experimentally) enters the kidney, is filtered and excreted.

thus measures amount of blood filtered by glomerulus

Question 9

in clinical practice, what is substance is used to measure GFR

Answer 9

creatinine - product of muscle breakdown

it is only slightly secreted by the body in negligible amounts

GFR measured gives slight overestimation

Question 10

Cockcroft - Gault equation for creatine clearance
age
weight
sex
creatinine

Answer 10

Creatinine clearance + (140 - age) * (kg) / (72 * creatinine)

Question 11

what do you use to measure renal plasma flow

Answer 11

PAH

both filtered and secreted and so calculating for clearance of PAH will determine renal plasma flow,

all of tha PAH that entered the kidney are 100% excreted in the urine

Question 12

why is there an Effective Renal Plasma Flow

Answer 12

PAH clearance would underestimate RPF because not all flow goes into the tubules, others may go to different areas of the kidney, thus called Effective RPF

Question 13

There is Renal Plasma Flow and there is Renal Blood Flow, what gives?

Answer 13

remember that there is plasma (55%), buffy coat (<1%), erythrocytes (45%)

Renal blood flow determined from RPF

Blood = plasma + cells/proteins

cells/proteins (%) = Hct (%)

Question 14

how do you solve for renal plasma flow?

solve for RPF if RBF is 10cc/min

Answer 14

RPF = RBF (1-Hct)

if renal blood flow is 10cc/min, composing of 60% plasma, 40% RBC/cells (hematocrit))

then,

RPF = 10 (1-.04)
= 6cc/min

Question 15

solve for RBF

RPF = 1L/min
Hct = 40%

Answer 15

RPF = RBF (1-hct) ;
RBF = RPF/ (1-hct)
= 1/ (1-.4)
= 1/(0.6)

RBF = 1.6 l/m

Question 16

effect of ACE inhibitors to GFR, RPF and FF

Answer 16

dilate efferent arteriole
decrease GFR (as more blood exited)
increased RPF
thus decreased FF