Lecture 56 - Physiological Adaptations to CKD

Question 1

what markers are used for tracking CKD?

why?

Answer 1

Cr and BUN

Cr - production rate is constant and relative to muscle mass
Production = filtration = elimination

Question 2

A patient with CKD has been eating a high salt diet, what happens and why?

what is the FeNa of a CKD patient?

Answer 2

Patient will become edematous

FeNa > 1%

With decreased GFR; slow to eliminate extra Na; positive Na Balance = EDEMA

Question 3

why is Urine Output a poor maker for kidney function

Answer 3

CKD: Cannot concentrate urine as well; but the body needs to excrete a minimum amount of solute per day

in order to do so – CKD patients might produce mcuh more urine

Question 4

Where does the bulk of K excretion come from? how might this be affected in CKD patients

Answer 4

K - excreted in the distal nephron (principle cells) by ROM K Channles –

Drugs that interefere with K secretion; CKD patients at risk for hyperkalemia

• eg: Spironolactone, ACE I

Question 5

H+ excretion with CKD:

what three factors alter H+ excretion

Answer 5

Decreased H+ excretion:

1) decreased NH4 generation
2) decreased HCO3 reclamation
3) Decreased ability to generate pH gradient

Question 6

Early CKD there is a ______Metabolic acidosis, due to _______

Later CKD there is a _______ metabolic acidosis, due to ______

Acidosis in part can lead to the development of _______
which can be partially treated by _______

Answer 6

• Early CKD: Non AG acidosis — decreased NH3 genesis

Late CKD: High AG Acidosis – decreased excretion of Titratable Acids

Renal Osteodystrophy (H+ balance bufffered by bones)

Can treat with HCO3 replacement

Question 7

Describe the pathogenesis of renal osteodystrophy

Answer 7

Kidney contains enzyme necessary for hydroxylation of Vit D to its active form (1,25 (OH)2 Vit D)

Decreased Vit: less gut absorption of Ca2+

Decreased PO4 excretion (chealator of Ca2+) = More PO4 in the serum; decreased Ca2+

Overall Less Ca2+ = Increased PTH activity (parathyroid hyperplasia)
Bone Re-absorption

Question 8

FGF 23 - what is it ? is it elevatd or decreased in Renal osteodystrophy?

Answer 8

New biomarker for RO

Normal role: acts on the kidney to increase PO4 excretion and decrease PTH activity

Kidney disease, receptors are destroyed, therefore FGF23 concentration elevated in RO

Question 9

how do you treat Renal Osteodystrophy?

Answer 9

Decrease PO4 intake
Use of PO4 gut binding resins 
Vit D replacment therapy 
Ca2+ receptor antagonists 
Parathyroidectomy

Question 10

iatrogenic disease resulting from therapies of RO

Answer 10

Adynamic Bone disease – too much PTH suppression

Osteomalacia: too much ALOH3 use (a chelator of PO4)

Question 11

how does CKD cause anemia

Answer 11

decreased EPO

Question 12

approach to treatment in CKD patients?

what is the go to long term drug therapy?

Answer 12

Treat the underlying disease (HTN, DM)

Long term drug therapy: ACE I, ARBs (prolongs progression to ERSD and need for dialysis)