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Kidneys > L10- CKD Clinical > Flashcards

L10- CKD Clinical Flashcards

1
Q

REMINDER: What are the normal endocrine functions of the kidney?

A

BP regulation

EPO

Ca-Phosp Balance and Vitamin D

Hormone Catabolism: Insulin!!

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2
Q

Why is Urea (BUN) an unreliable marker for kidney function and GFR?

A

Reabsorbed along the nephron

Urea clearance varies w/ hydration

Urea production rises w/ protein intake

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3
Q

what is the equation for eGFR?

A

see picture

Estimate ERRONEOUS if not in steady state - in other words if in AKI where things are changing

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4
Q

What is the staging of CKD based off of?

A

eGFR (see picture)

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5
Q

The Pcreat vs GFR curve is Hyperbolic. So what?

A

_ Early Disease - Proteinuria_

  • creatinine may not change at all early even tho you have lots of nephrons dying!! creatinine insensitive in early parts so small changes in Creatinine = LARGE loss of function and change in GFR

Later Disease - near ESRD on or not-on dialysis

  • can see LARGE changes in creatinine w/ small variation in GFR
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6
Q

What is the significance of FENA in CKD?

A

FENA = fraction of filtered load of Na that is excreted into urine

  • Kidney always trying to balance intake and output and so will excrete nased on dietary intake
  • In CKD, Filtered Load goes down
  • Therefore FENA goes up!!!

FENA is harder to maintain in CKD and changes in Na load can lead to Positive NaCL/volume balance or negative balance!!!

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7
Q

Why can there be high urine volume in CKD? What does that mean?

A

CKD

  • lose urinary concentrating ability and so takes more urine (less dilute) to excrete the same Osms/day
  • cant concentrate as well so takes more urine to get rid of same osmolarity

Therefore, high urine volume does NOT imply good renal function

In CKD, more you have to urinate then the worse are the kidneys

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8
Q

What’s the deal w/ K excretion in CKD?

A

Normally, all K is reabsorbed proximally and homeostasis depends on Distal K Secretion!!!

Therefore, CAUTION w/ CKD patients and drugs that change distal nephrons….can lead to Hyperkalemia!!!

ACE Inhibitors

Aldo Antag (Spironolactone, Eplerenone)

Amiloride - ENAC

**Type 4 RTA - Hyporeninemic Hypoaldosteronism **

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9
Q

What acid base disorder do people w/ CKD tend to get? why is that?

A

Downward drift on bicarbonate concentration bc kidneys can’t reclaim as much ….Metab Acidosis

1) Ability to generate NH4 limited - PCT
2) Ability to reclaim NaHCO3 limited - PCT
3) Ability to make pH gradient limited - CD

U in MUDPILES - Uremia

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10
Q

Why is Urine pH not a good measure of ability to acidify (excrete protons)?

A

NH4 is what counts!!

For a given pH, CKD patients excrete less ammonium ion and acidify urine more poorly….their Urine is more acidic but there is less NH4

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11
Q

How do you go from Non-AG acidosis to AG Acidosis in CKD?

Consequence of positive H+ balance?

A

Early CKD - non-AG Acidosis bc lower bicarb and less Nh3 genesis

Late CKD - less excretion of Titratable Acids!!!

Positive H+ balance is bad for bones and favors early osteodystrophy

Treatment: NaHCO3 oral replacement

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12
Q

Describe the progression of CKD w/ the changes in this graph:

A

GFR decreases = Kidney disease progression

1,25 Vit D - falls bc kidney not converting it

25 Vit D stays the same bc in proportion to diet and liver functoin

Phosphorous - accumulates bc kidney can’t excrete it and it chelates calcium so perceived low calcium increases PTH release

Parathyroid hyperplasia + Bone degradation

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13
Q

Describe Vitamin D metbaolism and what happens in CKD?

A

D3 made into 25OHD3 in Liver (excess) and then 1,25OH2D3 (calcitriol) made in kidney by enzyme 1-Hydroxylase

1-Hydroxylation falls in early CKD (GFR<80) and have to give oral Calcitriol

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14
Q

What does PTH normally do?

A

Released by PT glands in response to low calcium

  • Liberates Ca from bone (and phosphate) by activating osteoclasts
  • increases renal conversion of Vitamin D so can absorb more Ca from gut
  • Decreases phosphate reabsorption by the PCT in the nephron so excrete more
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15
Q

What happens in CKD to all the normal PTH functions?

A

Increased PTH from low calcium and then get

  • increased bone degradation from PTH
  • Plasma phosphate rises bc kidney can not respond and excrete more in response to PTH
  • Plasma phosphate chelates calcium and lowers free Ca concentration so more PTH released
  • therefore, degrading bone to increase CA but can’t sense it bc increase phosphate bc kidney can’t excrete it *
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16
Q

What is FGF23?

A

Fibroblast Growth Factor 23

Signals to the PCT to take away phosphate reabsorbing transprters and blocks PTH release

in CKD, target effects are REDUCED and so still reabsorbing a lot of phosphate

17
Q

What are signs and symptoms of renal osteodystrophy?

A

Bone pain

Pathoogical fractures

ITCHING

Skeletal deformities - Rickets in kids

Growth retardation

Vascular and Tissue Calcification - Calciphylaxis

18
Q

What is Osteitis Fibrosa Cystica? What do you see w/ that? How do you treat it?

A

PTH EXCESS!!!!

Increased bone turnover

See Subperiosteal Bone reabsorption

Treatment: want ionized Ca in blood to increase

  • Lower phosphate intake
  • bind phosphate in the gut - Al, Ca, La, Sevalamer
  • Vit D replacement
  • CA receptor Agonist - Calcimimetic agaent to trick Parathyroid
19
Q

What is the risk of treating people for Osteitisi Cystica and CKD?

A

Adynamic Bone Disease

Too much PTH suppression from treatment of PTH excess - therefore in CKD aim for high or slightly elevated PTH levels

20
Q

What is osteomalacia?

A

Failure to mineralize new osteoid

Iatrogenic from Aluminum Salts (not relaly used anymore)

21
Q

Why do you get anemia in CKD? how do you treat it?

A

Anemia - from low EPO production and so see low HCT

Treatment - Recombinant EPO

22
Q

What’s the best thing to do to prevent progression of renal disease?

A

BP CONTROL!!!

ACE inhibitors and ARBs - lower GFR and BP and both are good for kidneys

  • lower GFR means less protein in PCT (PCT tries to absorb protein and then gets stuck in interstitium and then get inflammation and MORE kidney damage) so here lowering GFR in CKD is protective for kidneys

Kidneys (13 decks)

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