L57 Flashcards
Is Cr or BUN (urea) produced at a constant rate?
Cr
BUN det by protein intake and catabolism: unreliable marker of GFR
What happens to Cr as GFR drops?
HYPERBOLIC curve
Large ↓GFR is masked by small changes in Cr
What is eGFR?
Estimated GFR
Takes Cr, age, gender, weight and race into account
ONLY use in steady state
What lab value is used to stage CKD?
eGFR
What is the Cr during CKD stage 1?
eGFR = 90+
Early CKD - Cr may not change at all (L hyperbolic curve)
Realize small changes = large losses in fxn
The healthy nephrons hypertrophy to take the load from damaged ones
What does Cr tell you in late CKD?
Large shifts in Cr for small changes GFR
R side hyperbolic curve
How does the kidney’s handling of Na change in CKD?
Goal is the same during healthy or disease: Na in = Na out
See ↑FE Na
FE Na - same Na / less filtered load
You must excrete more of the filtered load because you’re now less effective
How does a CKD do to adapt to high Na intake?
Can elim the excess Na but takes longer
Leave you in +Na balance = edema
What does a CKD kidney do to adapt to low Na?
↓U Na - takes longer
Excess restriction = (-)Na balance -> hypovolemia
How does water excretion change in CKD?
Can’t max [ ] or dilute
If you can’t [ ] urine, you must pee more volume to get the same amt solute out
↑Minimum daily urine vol
Why does high urine volume NOT imply good renal fxn in CKD?
B/c less urine [ ] means more volume is need to excrete a normal amt solute
Which part of the nephron determines L homeostasis?
CD
All K is reabsorbed at PCT
Therefore depends on the ability to secrete K @ CD
Do you become alkalotic or acidemic during CKD progression? 3 reasons why
Metabolic acidosis
- Can’t reclaim bicarb (PCT)
- Can’t NH4 (PCT)
- Can’t generate pH gradient (CD)
What is the best measure of kidney H+ secretion?
U NH4 > pH
Is the metabolic acidosis during CKD gap or non-gap?
Early: non-gap
Late: gap b/c not excreting titratable acids
How does acidemia effect the bones? Treat
Osteodystrophy
+ PO bicarb
Why does 1,25 vit D drop as ↓GFR?
B/c kidney does the 1 hydroxylation
Can’t make 1,25 vit D = calcitriol
↓Reabsorption of Ca from gut
Fails early in CKD
3 normal fxn PTH
- Release Ca2+ from bone
- ↑25 -> 1,25 vit D @ kidney
- ↓Phosphate reabsorption by kidney
What are the 2 factors that lead to ↓P Ca in CKD?
↓1,25 vit D - ↓Ca from gut
↓PO4 excretion - ↑ in plasma
What are the effects of ↓Ca?
↑PTH
- ↑Osteoclast = ↑P Ca
- Reabsorb @ kidney (dysfxn)
What is FGF23? How does it effect PTH + phosphate?
Phosphatonin = stim phosphate excretion via urine to raise blood Ca
↓FGF23 in CKD: ↓PTH, ↑phosphate
Signs + symptoms of renal osteodystrophy
Pain: low back, hips, knees Pathologic fx Pruritis Vasc + tissue calcification Rickets + growth retardation - kids
What is a negative SE of tissue calcification?
Calciphylaxis = thrombosis + skin necrosis
What is osteitis fibrosa cystica? Appearance on XR
PTH excess: bone formation + reabsorption
XR: subperiosteal bone reabsorption
Treat osteitis fibrosa cystica
- ↓Phosphate intake//bind whatever is in diet @ GI
- +1,25 vit D
- Ca receptor antag
Extreme: parathyroidectomy
What happens if you suppress PTH too much?
Adynamic bone disease - too brittle, can’t adapt
What is osteomalacia?
Failure to mineralize new osteoid
Artifact of old meds - not as relevant
Treat CKD anemia
Recombinant EPO
Treat slowly progressing CKD
BP + diabetes/glucose control
ACE I or AGT receptor blockers
