04 Renal Physiology II
- actual calculation
- GFR: main number for kidney healthiness
- 40% going across glomerulus, 60% leaving kidney
- actual calculation
- GFR: main number for kidney healthiness
- how much Na going across glomeruli per min
- urine flow: how much urine kidney making
- urine flow rate: how much urine pt makes
Clearance
- urine concentration, urine flow rate , plasma concentration
- kidney cleared 5 mole of Na OR
- kidney cleared 1L of blood of Na
GFR
- inulin
- creatinine
- all filtered inulin goes out of kidney
- naturally clearing, easier to do
- Volume flow cumbersome to determine
- special formula to use
- amount in urine = amount made in muscles
- not a linear, straight line relationship
- plasma Cr concentration, not urine concentration
- use clearance equation to calculate GFR if given urine/plasma concentration and urine flow
RPF
- small amount goes to CT
- everything in goes out, none in the efferent
- calculate amt of blood filtered of PAH (clearance), one can find amt of blood enter kidney
RBF
- HCT = bottom red
Others
Meds
- FF same: still filtering same percentage of blood
- pt can go into renal failure/heart failure
- Ang II: constrict efferent, increase GFR, decrease RBF
Secretion and Absorption
- if filtered not = excretion, some must be either secreted or reabsorbed
- if put in 10 grams, must excrete 10 grams, otherwise accumulate
Normal:
- 5 in, 5 out, 4 plasma concentration
-
insult: can't excrete, 5 in, 2 out, plasma concentration go up to 6
-
new steady state, 5 in, 5 out, 6 plasma
-
new steady state concentration higher than original steady state
-
e.g. hyperkalemia, excreting same amount taking in
- filtered load: GFR x plasma concentration for urea is same
- fractional excretion: excretion/filtered load, filtered load fallen, amt excreted is same
- 5 g filtered, 1 secreted, fractional excretion: 1/5
- renal failure, GFR fallen
- 2 g filtered, 1g excreted, fractional excretion 50%
Practice Questions
- clearance of inulin = GFR
