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CRRAB II Final > Renal Basics > Flashcards

Renal Basics Flashcards

1
Q

What is Homeostasis?

A

Property of a system that is regulated so internal conditions are stable and relatively constant!

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2
Q

What are the nine main fxns of the Kidney?

A
  1. Filtration (Clearance of Na+, drugs, creatinine, Urea, H+)
  2. Maintaining blood pressure
  3. Na+ homeostasis (volume)
  4. H2O homeostasis
  5. K+ homeostasis
  6. Bone/mineral homeostasis (VitaD, PO4-)
  7. Acid-Base homeostasis
  8. RBC production & regulation (EPO = erythropoietin)
  9. Gluconeogenesis (kidney is also an endocrine organ)
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3
Q

What can the kidney sense very small changes in?

A

Oxygen levels!

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4
Q

How many glomeruli do premees have? What does some evidence suggest?

A

-Fewer glomeruli than normal baby (

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5
Q

How much of the cardiac output goes through the kidney on first pass?

A

20%! (~1000 ml/min blood)

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6
Q

What other structures have more blood flow per gram weight than kidney?

A

Brain (maybe liver)

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7
Q

What is the blood composed of?

A

40% RBC

60% Plasma

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8
Q

What does protein in the urine indicate?

A

KIDNEY DAMAGE

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9
Q

What is the Renal Plasma Flow (RPF)?

A

600 ml/min

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10
Q

What are two mechanisms by which the glomerulus restricts what it filters?

A
  1. Size

2. Charge

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11
Q

What three components of the glomerulus helps restrict filtering by size?

A
  1. Capillary Endothelium
  2. Basement Membrane
  3. Podocytes
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12
Q

How does the Capillary Endothelium restrict filtering?

A
  • It’s 10% pores & fenestrations

- -> Anything but cells & protein go through

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13
Q

How does the Basement Membrane restrict filtering?

A

It’s ANIONIC (negative charge)

  • Anionic component = heparin sulfate proteoglycan
  • Type IV collagen network - like a sponge!
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14
Q

How do Podocytes restrict filtering?

A

These are cells exterior to the basement membrane forming small, negatively charged slits.
-Can form slit diaphragms that block the absorption of large molecules!

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15
Q

What sizes and molecules are freely filtered?

A

Anything

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16
Q

What is normally NOT filtered?

A

Anything > 70,000 D

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17
Q

How big is albumin?

A

66,000 D –> some but very little can get through the glomerulus

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18
Q

How does charge prevent filtration in the glomerulus?

A

GMB & Slit diaphragms are negatively charged; hence, anionic particles filter less well than cationic!

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19
Q

What is the definition of GFR?

A

Glomerular filtration rate.

-Movement of fluid and solute across from the capillary lumen into Bowman’s space across all glomeruli in both kidneys

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20
Q

What does a reduced GFR indicate?

A

Tells us the kidney’s ability to filter is reduced/subpar/below where it should be

21
Q

Why does pi*bs = 0 most of the time?

A

There is NO ONCOTIC pressure in the Bowman’s space!

22
Q

What is the normal GFR?

A

180L/day

23
Q

What is the renal plasma flow (RPF) into the glomerulus and out of?

A

600 ml/min in

475 ml/min out

24
Q

How much does the glomerulus filter out per day?

A

2L/day

25
Q

What does NE do the afferent and efferent arterioles of glomerulus?

A

Vasoconstricts

26
Q

What does Angiotensin II do the afferent and efferent arterioles of glomerulus?

A

Vasoconstricts

-More influence on the efferent arteriole

27
Q

What do PGE (prostaglandins) do the afferent and efferent arterioles of glomerulus?

A

Vasodilates!

28
Q

What is the mechanism of Tordol?

A

Inhibits prostaglandins, causing vasoconstriction of glomerular capillaries

29
Q

What is the mechnaism of ACE inhibitors?

A

Inhibit Angiotensin II, causing vasodilation of glomerular capillaries

30
Q

What happens to RPF and GFR when you Vasoconstrict the afferent arteriole of glomerulus?

A

GFR decreases.
RPF decreases.
Pressure in glomerular capillaries decreases.

31
Q

What happens to RPF and GFR when you Vasodilate the afferent arteriole of glomerulus?

A

GFR increases.
RPF increases.
Pressure in glomerular capillaries increases.

32
Q

What happens to RPF and GFR when you Vasoconstrict the efferent arteriole of glomerulus?

A

GFR stays the same or increases.
RPF decreases.
Pressure in glomerular capillary increases.

33
Q

What happens to RPF and GFR when you Vasodilate the efferent arteriole of glomerulus?

A

GFR decreases.
Pressure in glomerular capillary decreases.
RPF likely decreases.

34
Q

What is the filtration fraction?

A

Percentage of renal plasma flow that is freely filtered.

20%!! (Na+, Cl-, Bicarb., etc.)

35
Q

How do you calculate the filtered load?

A

[Xserum]*GFR
-Different for every ion/thing!
Sodium = 140 mEq/L x 180 L/day = 25,000 mEq Na+/day

36
Q

How do you calculate the excretion rate?

A

[Xurine]*UFR

  • Should always be what is necessary to keep you in balance!
    2. 5 L/day * 200 mM/day = ~4.5 grams Na+
37
Q

What does glucose in the urine indicate?

A
  1. You’ve damaged the tubule.

2. You’ve exceeded the amount of glucose you can absorb.

38
Q

What happened to the RPF and GFR in the old lady on NSAIDS and ACE inhibitors?

A
  1. NSAIDS –> inhibit PGE and cause vasoconstriction of the efferent arteriole.
  2. ACEi —> Inhibit Angiotensin II and cause vasodilation of the afferent arteriole.
  3. These two combined cause Decreased RPF, Decreased GFR and decreased Pressure in the glomerular capillary.
39
Q

What are some examples of special circumstances where the Filtered Load (FL) = Excretion Rate (ER)?

A

Solute is completely filtered (no reabsorption).

Creatinin, Inulin, Iohexol

40
Q

What is the equation for GFR?

A

([X]urine * UFR) / [X]serum = ERsolute/Plasma conc. of solute

41
Q

What are the two ways you can use Creatinine to estimate kidney function?

A
  1. Measure CrCl directly

2. Estimate CrCl

42
Q

How do you measure Creatinine Clearance directly?

A

CrCl = measurement of a 24 hr urine.

  • It assumes a steady state
  • Only used in very specific clinical circumstances
  • Good test, but rarely collected appropriately
  • Need to order a urine creatinine to determine if it was collected appropriately
43
Q

How much Creatinine should someone produce in a day?

A

1,440 mg/day = ER = UFR*[X]urine

44
Q

What is the normal Creatinine production for a male and female?

A

~25 mg/kg/day = male

~20 mg/kg/day = female

45
Q

What two equations are not valid if renal function is near normal?

A
  1. Cockcroft-Gault

2. MDRD (designed from modification of diet in renal disease study)

46
Q

How can you estimate CrCl?

A

Cockcroft-Gault Equation:

[(140-age) (wt in kg) (.82 if female)] /72*Serum Cr

47
Q

How can you estimate GFR?

A

Use MDRD!

GFR = 186.3 x Serum Cr (exp[-1.154]) x Age(exp[-0.203]) * (0.742 if female) * (1.21 if black)

48
Q

What problems are associated with using Creatinine as an estimator?

A

Creatinine will be secreted at a variable amount depending on renal function!
-10-40% is secreted
-Secretion will ramp up in early phases of GFR decline
[General rule of renal fxn falling by 1/2, Creatinine doubles, doesn’t work in early phases]

CRRAB II Final (10 decks)

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